INDEPENDENCE, Mo.>> Christopher Hixon, a 27-year veteran of the Navy who served in the Persian Gulf, trained with government ammunition that typically had a distinctive “LC” marking on its brass casings.

In 2018, Hixon, then the athletic director at Marjory Stoneman Douglas High School in Parkland, Fla., confronted a former student firing an AR-15-style gun. The semi-automatic rifle, modeled on a military weapon, was loaded with ammunition carrying the same “LC” stamp.

Hixon took a bullet in a thigh. Two more hit him in the chest. In the bloodstained hallway where he died, investigators found a brass casing. And another. By the end of their search, they had collected 84 from across the school — each marked “LC.”

The initials stand for the Lake City Army Ammunition Plant. Built during World War II, the federal site, in Independence, Mo., has made nearly all the rifle cartridges used by the U.S. military since it pulled out of Vietnam.

In recent years, the factory has also pumped billions of rounds of military-grade ammunition into the commercial market, an investigation by The New York Times found, leaving the “LC” signature scattered across crime scenes, including the sites of some of the nation’s most heinous mass shootings.

The plant, operated by a private contractor with Army oversight, is now one of the country’s biggest manufacturers of commercial rounds for the popular AR-15, and it remains so even as the United States supplies ammunition to Ukraine.

The vast majority of Lake City rounds sold by retailers have gone to law-abiding citizens, from hunters and farmers to target shooters. Some are drawn to them because they are made with the same materials and often to the same specifications as the military’s, while others see them as an authentic accessory for their tactical weapons and gear.

But more than 1 million pages of search warrants, police evidence logs, ballistic reports, forfeiture records and court proceedings compiled by the Times provide a sweeping accounting of how Lake City ammunition, once intended for war, has also cut a criminal path across towns and cities in nearly all 50 states.

A former Marine used Lake City rounds in the murder of two police officers and a deputy sheriff in Louisiana. Police recovered spent Lake City casings after a former justice of the peace killed a Texas district attorney and his wife. In Washington, a barrage of gang-related gunfire left the courtyard of an apartment complex littered with more than 40 “LC” casings and a 10-year-old girl dead.

In May, a high school student armed with ammunition from the plant rampaged through a residential neighborhood in Farmington, N.M., killing three and injuring six.

Lake City rounds have been seized from drug dealers, violent felons, anti-government groups, rioters at the U.S. Capitol and smugglers for Mexican cartels. They were confiscated from a man in Massachusetts who threatened to assassinate President Barack Obama and from a man at Los Angeles International Airport after he fired at a civilian and three Transportation Security Administration agents, killing one.

Starting in 2012 with the massacre of 12 people at a movie theater in Aurora, the rounds have been tied to at least a dozen mass shootings involving AR-15-style guns, including at the Tree of Life synagogue in Pittsburgh; the Robb Elementary School in Uvalde, Texas; a FedEx warehouse in Indianapolis; and Marjory Stoneman Douglas High School. Authorities in Lewiston, Maine, declined to release ballistic information about the mass shooting there last month that resulted in 18 deaths.

Payton Gendron, who was sentenced to life in prison for killing 10 and injuring three at a Tops supermarket in Buffalo, N.Y., had mentioned Lake City in his manifesto and online diary. He planned to fire at a security guard through a window, he wrote, and the rounds made at Lake City were “the best barrier penetration ammo I can get.” The guard, a retired police officer named Aaron Salter Jr., was killed as he tried to stop the assault.

The availability to consumers of rifle cartridges made at an Army site is the fruit of a symbiotic relationship between the Defense Department and the ammunition industry. A legacy of the war on terror, the federal contract to operate Lake City’s sprawling manufacturing campus is intended to save taxpayers money while keeping it ready to ramp up at a moment’s notice.

When the military needs ammunition, the contractor is required to make it, but it is otherwise free to keep production lines humming with commercial operations.

Over the last two decades, the government has invested more than $860 million to improve and repair the plant and expand its capacity, according to Justine Barati, an Army spokesperson. The Army has also required Lake City contractors to pick up some costs. Under the current arrangement, the contractor has covered at least $10 million a year in improvements — an amount that can grow, depending on production levels. The payments are earmarked for projects ranging from office renovations to equipment upgrades.

The Defense Department argues that the public- private partnership is necessary for national security.

“We don’t maintain and/or improve our ammo plants because it’s ‘economical’ to do so,” Doug Bush, an assistant secretary of the Army in charge of acquisitions, said in a statement. “We do it to ensure we have government-owned production capacity for military-specific items that we can surge in case of a conflict.”

A Defense Department official, in a statement, said “commercial utilization brings lower costs to the Army and taxpayer, and keeps a skilled work force better positioned to respond to surge requirements.” The official said a 2021 study found that the government received a 10% to 15% discount on ammunition by allowing commercial sales.

The trade-off for ordinary Americans is that commercial ammunition for the AR-15 is being manufactured in large quantities on government property with little or no public accountability as to how it is marketed and sold.

Secrecy around the arrangement has helped to hide its scale, and the Army has played down the plant’s role in manufacturing ammunition for civilians. A recent media tour of Lake City focused on its military operations and economic benefits to the region but did not include access to the building where most commercial rounds are made.

Behind closed doors, the possibility of Lake City ammunition’s appearing in high-profile crimes was a source of continuing concern for the plant’s contractors, according to four former employees who were not authorized to speak publicly. After mass shootings, in particular, managers were “terrified” that journalists might discover a connection to the site, one of the former employees said.

The current contractor, Olin Winchester, which began running Lake City in October 2020, is required to regularly file reports to the Army on commercial production and sales. While the information is not classified, it is closely guarded. Military officials described it as proprietary and recommended requesting details from Olin Winchester, which did not respond to emails or phone calls from the Times.

By reviewing annual reports, earnings-call transcripts and government documents and interviewing more than 40 former employees and others with knowledge of Lake City’s operations, the Times was able to determine that the site had manufactured hundreds of millions of rounds for the commercial market every year since at least 2011.

For most of that period, its commercial operations outstripped its military business. By 2021, commercial output — which includes retail sales as well as purchases by law enforcement agencies and foreign governments — had outpaced military production by more than two times, according to a historical overview the Army provided in a graphic during the media tour. Later, the Army declined to share the underlying data and at one point denied the graphic existed.

The .223-caliber and 5.56 mm cartridges — the most common rounds for the AR-15 — have been sold under a variety of brands at stores and through websites. Even spent Lake City casings have a robust market because of their quality. A federal investigation after the 2017 shooting that killed 60 and wounded hundreds more at a country music festival on the Las Vegas Strip found that the gunman had bought Lake City casings that had been reloaded with new primers, powder and bullets.

In a 2021 earnings call for Olin Winchester’s parent company, analysts said that ammunition profits far exceeded projections. Executives credited the Lake City contract.

“Not only has it become part of our military business,” said Scott Sutton, the top executive at the company, Olin Corp., “but also part of our commercial business.”

In a statement to the Times, Federal Cartridge, a distributor of Lake City’s ammunition at the time of the Parkland shooting, condemned the “criminal misuse” of its products. In its response to questions, the Defense Department did not address the use of Lake City ammunition in mass killings and other crimes but said “there is currently no plan” to end commercial sales.

“Flawlessly reliable”

The story of how a government-owned ammunition plant became one of the world’s largest producers of commercial rounds for semi-automatic rifles begins with World War II.

The need for wartime ammunition far exceeded American industry’s ability to make it, so the federal government built dozens of factories and paid companies to run them. Construction began in Lake City in the winter of 1940 with a shovel full of dirt from Harry S. Truman, then a senator from Missouri.

At the end of the war, Lake City temporarily closed its doors, and for decades, production followed a similar pattern: When U.S. troops fought in Korea and Vietnam, billions of rounds flowed from the plant, while in peacetime, manufacturing ebbed. After the Cold War, production dropped to a few hundred million rounds a year.

The terrorist attacks of 9/11 jolted Lake City back into action. Mothballed equipment was pulled out of crates, and the Army paid nearly $50 million to expand production. Other U.S. manufacturers had the capacity to make just 300 million rounds of the ammunition it required, the Army found, compelling it to look abroad for more.

An Army general, called before Congress, pledged not to repeat the mistake of “building capacity during wartime only to dismantle the capacity in peacetime.”

One possible fix, described in a government report, was to keep the equipment at the ready but adjust the number of work shifts to the rhythms of war.

The contractor at the time, ATK, or Alliant Techsystems, favored a different solution, according to people familiar with the discussions: When military demand fell, the company would fill the shortfall with rounds to be sold commercially.

In the early 1990s, a law aimed at cutting defense budgets had made it legal to conduct commercial business at certain government-owned defense installations. A previous Lake City contractor had sold some ammunition to the public, and ATK continued the practice, using packaging from Federal Cartridge, a respected ammunition maker it acquired in 2001.

The rounds quickly found a cult following among fans of military-style weapons.

In a 2006 earnings call, Daniel Murphy Jr., a retired admiral who was ATK’s CEO, explained that softening military demand would leave Lake City with excess capacity for the company to fill. “We are looking hard right now at the international market and, frankly, other markets,” including domestic sporting and law enforcement, he said.

The shift came at an inflection point for the firearms industry. A nationwide assault weapons ban had expired in 2004, bringing a fresh customer base into view: the rapidly growing ranks of gun owners enamored with military-style weapons.

“Record backlogs”

With the election of Obama as president in 2008, fears of new gun control measures fueled a boom in semi-automatic rifle purchases, and ammunition makers could not keep up.

In a call with analysts that year, Murphy cited “record backlogs” at ATK’s other plants and said Lake City had an opportunity to pick up sales. But, he cautioned, “we are going to have a hard time in explaining it to the general public.”

In 2009, Army officials added a clause to the Lake City contract requiring a capacity of 1.6 billion rounds. Keeping the plant hot with commercial sales was the most obvious solution because its machinery, once stopped, could take weeks or longer to come back online, and continuous production would also keep workers at the ready, according to interviews.

As the plant’s commercial operations took off, some of its products had already found their way into the criminal underworld. In 2009, FBI agents disrupted a plot by homegrown jihadis in North Carolina to attack the Quantico Marine Corps Base. A search of one of their homes uncovered an empty Lake City ammunition box.

By the time ATK’s contract came up for bidding again in 2011, the company was selling hundreds of millions of Lake City rounds a year to retailers and other commercial customers, according to earnings reports and government documents.

Awakened to the booming demand for the plant’s products, the Army directed contractors to include proposals for selling its excess capacity in their new bids. The decision would “incentivize commercial use in the plant, creating a win-win for the contractor and the government,” an article in an internal Army magazine said, predicting the new requirement would save taxpayers as much as $900 million on ammunition over 10 years by driving down costs for the Pentagon.

ATK won the competition as its new CEO, Mark DeYoung, moved the company further into the market for popular tactical weapons and gear, aiming to become a “one-stop shop” for shooting-sports enthusiasts. ATK was acquiring a series of firms that manufactured optics, holsters, combat vests and other accessories that appealed to owners of AR-15s, many of whom wanted to emulate U.S. troops in Afghanistan and Iraq.

In a 2015 interview with Outdoor Life, DeYoung traced the strategy to Lake City. “I recognized that if we could build a business around shoulder-fired ammunition for the military,” he said, “we could do the same thing for the consumer market.”

That consumer market included a neuroscience graduate student at the University of Colorado who would set off a new era of mass shootings — those carried out with AR-15-style rifles.

Mass shootings, mass sales

In June 2012, James Holmes, the Colorado graduate student, ordered 1,500 rounds of Lake City ammunition from the website BulkAmmo.com, which had been offering discounts on boxes of the 5.56. He had them delivered to a FedEx shipping center near his home.

The next month, Holmes stormed into a Century 16 cinema theater in Aurora, wielding an AR-15-style rifle loaded with the ammunition and dressed in an “urban assault vest” sold by an ATK subsidiary. He killed 12 people and wounded 70 in what was the deadliest mass shooting to date with an AR-15-style gun, according to a database maintained by the Violence Project. The tally includes shootings in a public place in which four or more people, not including the attacker, were killed.

Later that year, another gunman armed with an AR-15-style rifle killed 26 pupils, teachers and staff members at Sandy Hook Elementary School in Newtown, Conn. He did not use rounds from Lake City, but the tragedy drove a new push for gun reform — and a reflexive spike in ammunition sales.

In 2014, Lake City’s production reached a record high of nearly 2 billion rounds. Less than half went to the military, Army data shows. Many of the rest poured onto shelves at big-box retailers, helping drive a $300 million annual increase in sales for ATK, according to earnings statements. Black Friday at Walmart and other stores made preparations for the Thanksgiving holiday one of the busiest and most stressful times at the plant, according to two people familiar with its operations.

When ATK merged with the aerospace company Orbital the following year, ATK’s sporting division was spun off as Vista Outdoor. Led by DeYoung, Vista received a three-year exclusive contract to sell Lake City’s commercial products.

DeYoung did not respond to requests for comment.

In early 2015, the national gun debate brushed against Lake City for the first time as the Bureau of Alcohol, Tobacco, Firearms and Explosives moved to restrict civilian availability of one of the plant’s products, a variety of 5.56 rounds known as “green tips.”

The rounds had been adopted by U.S. forces for their ability to punch through steel helmets and light body armor at long distances, but in 2010, the Army had begun replacing them with a more lethal round that was not available to the general public.

The ATF announced that it was considering limiting the availability of green tips under a law intended to protect law enforcement officers. It sparked a firestorm. The agency received more than 80,000 public comments opposing the idea as well as harsh criticism from the gun industry and members of Congress who said it violated the Second Amendment.

The ATF backed down. Within a year, Lake City green tips were tied to the shooting of five police officers and a deputy sheriff.