SUTHERLAND SPRINGS, Texas — A gunman clad in all black, with a ballistic vest strapped to his chest and a military-style rifle in his hands, opened fire on parishioners at a Sunday service at a small Baptist church in rural Texas, killing at least 26 people and turning this tiny town east of San Antonio into the scene of the country’s newest mass horror.

The gunman was identified as Devin Patrick Kelley, 26, according to two law enforcement officials who spoke on the condition of anonymity because the investigation is continuing. Kelley, who lived in New Braunfels, was discharged from the Air Force for allegedly assaulting his wife and child, the Associated Press reported, citing an Air Force spokeswoman. He died shortly after the attack on the church.

The motive of that attack was unclear Sunday, but the grisly nature of it could not have been clearer: Families gathered in pews, clutching Bibles and praying to the Lord, were murdered in cold blood on the spot.

The gunman started firing at the First Baptist Church in Sutherland Springs not long after the Sunday morning service began at 11 a.m. Central time, officials said. He was armed with a Ruger military-style rifle, and within minutes, many of those inside the small church were either dead or wounded. The victims ranged in age from 5 to 72, and among the dead were several children, a pregnant woman, and the pastor’s 14-year-old daughter.

It was the deadliest mass shooting in the state’s history. At least 20 more were wounded.

“It’s something we all say does not happen in small communities, although we found out today it does,’’ said Joe Tackitt, the sheriff of Wilson County, which includes Sutherland Springs.

Tackitt and other officials said the gunman began firing from the outside, moving to the right side of the church. Then he entered the building and kept firing.

The authorities received their first call about a gunman at about 11:20 a.m. Officials and witnesses said he appeared to be prepared for an assault, with black tactical gear, multiple rounds of ammunition, and a ballistic vest.

When the gunman emerged from the church, an armed neighbor exchanged gunfire with him, hitting the suspect, who fled in his vehicle. Neighbors apparently followed him, chasing him into the next county, Guadalupe, where he crashed his car. The gunman was found dead in his vehicle. Officials said it was unclear how he had died.

At the church, he left behind a scene of carnage. Of the 26 fatalities, 23 people were found dead inside the church, two were found outside, and one died at a hospital.

In nearby Floresville, hours after the attack, Scott Holcombe, 30, sat with his sister on the curb outside the emergency room at Connally Memorial Medical Center. They were both in tears. Their parents, Bryan and Karla Holcombe, had been at the church. They were dead.

“I’m dumbfounded,’’ Holcombe said. “This is unimaginable. My father was a good man and he loved to preach. He had a good heart.’’

His sister, Sarah Slavin, 33, added: “They weren’t afraid of death. They had a strong faith, so there’s comfort in that. I feel like my parents, especially my mom, wasn’t scared.’’

A parishioner, Sandy Ward, said that a daughter-in-law and three of her grandchildren were shot. Her grandson, who is 5, was shot four times and remained in surgery Sunday night. She said she was awaiting word on her other family members.

Ward said she did not attend services Sunday because of her troubled knees.

At a news conference Sunday, Governor Greg Abbott said he and other Texans were asking “for God’s comfort, for God’s guidance, and for God’s healing for all those who are suffering.’’

President Trump, who was in Japan on a trip to several Asian countries, called it a “horrific shooting.’’

In a time of crisis, he said, “Americans will do what we do best: We pull together and join hands and lock arms and through the tears and sadness we stand strong.’’

The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were helping in the investigation, which was being led by the Texas Rangers.

The shooting unfolded on the eighth anniversary of the attack in 2009 on Fort Hood in Texas, when an Army psychiatrist, Major Nidal Malik Hasan, killed 13 people in one of the deadliest mass shootings at a US military base. Hasan carried out his attack in an attempt to wage jihad on American military personnel.

The shooting Sunday occurred more than two years after Dylann S. Roof opened fire at Emanuel African Methodist Episcopal Church in Charleston, S.C., in June 2015, killing nine people, including the pastor. The motive in that attack was racial hatred — Roof, a white supremacist, plotted an assault on a black congregation — but no motive has been established by the authorities in the shooting in Sutherland Springs. The First Baptist Church is predominantly white, and Kelley is white.

The authorities said Kelley used an Ruger AR-15 variant — a knockoff of the standard service rifle carried by the US military for roughly half a century.

Almost all AR-15 variants legally sold in the United States fire only semi-automatically and were covered by the federal assault weapons ban that went into effect in 1994. Since the ban expired in 2004, the weapons have been legal to sell or possess in much of the United States and sales of AR-15s have surged.

Ruger’s AR-15s made for civilian markets sell for about $500 to $900, depending on the model.

The shooting is sure to add impetus to the call for tighter gun control laws.

“When a shooter guns down innocent children and families in a holy place, there can be no rest. Congress must act now to stop gun violence,’’ said Senator Edward Markey, Democrat of Massachusetts.