Juana Espino went to Copeland Street Saturday afternoon looking for answers.

Shortly after midnight, an argument at a house party on that Roxbury street turned violent and four men were shot, police said. Among the victims, Espino said, was her 34-year-old son, who was struck in the hand.

“We don’t really know what’s going on,’’ said Espino, 62, as she headed into an apartment building to speak with her son. “He’s really mad. His right hand is messed up.’’

The Roxbury shooting was part of a violent night during which gunfire also wounded men in Mattapan and Dorchester.

In Mattapan, a man in a vehicle near a Burger King at 875 Cummins Highway was shot and seriously wounded in his upper body at 11:56 p.m. Friday, police said.

Less than an hour later, at 12:45 a.m. Saturday, a bullet grazed a 25-year-old man on Elder Street in Dorchester, said Officer Kim Tavares, a police spokeswoman.

“In Boston there are so many shootings,’’ Espino said. “You don’t know who’s shooting who.’’

As of Saturday evening, none of the victims had died, according to police, and no arrests had been made.

Police Commissioner William B. Evans was on Copeland Street shortly after that shooting. He said officers were summoned at 12:09 a.m. to the scene, where they encountered a belligerent crowd. At least two suspects were seen fleeing on foot. The victims were believed to range in age from mid-20s to mid-30s, he said.

In addition to Espino’s son, Evans said that three other men shot were taken to local hospitals after suffering more serious wounds.

“One’s very, very serious,’’ Evans said. “We’re hoping he makes it.’’

Mayor Martin J. Walsh said later Saturday that the shootings occurred at “a house party gone bad,’’ and urged witnesses to cooperate with investigators. Hours before the shootings, Walsh and Evans had participated in a peace walk in Roxbury with several mayors who are in Boston for the annual meeting of the US Conference of Mayors.

“There could have been a lot of loss of life there,’’ said Walsh, who spoke at the Boston Marriott Copley Place, where he is hosting the gathering.

“It’s hard to do an investigation of a situation, an incident like that, where there [are] clearly people involved and witnesses that aren’t willing to talk,’’ he said. “Assistance there would be helpful.’’

Walsh blamed much of the rash of violence in Boston on illegal guns. While Massachusetts has strong gun laws, he said, the federal government must step up with implementing stronger regulations.

He drew a direct connection between street-level gun violence in Boston and mass shootings in places like Parkland, Fla., and Las Vegas.

“There is a common theme here. The federal government has refused to deal with the issue of loss of life,’’ Walsh said. “They say the right things and they tweet the right things, but they are clearly not interested in trying to save young people’s lives in America.’’

Evans also asked for the public’s help in solving the Copeland Street shootings.

“There are people who knew who did it. We need them to step up,’’ said Evans, who attended the mayoral conference to discuss gun violence.

He gave the example of a shooting Friday afternoon in Codman Square, where witnesses spoke with detective, and police were able to secure a warrant for the suspect.

The Rev. Ruthanne Bracey-Darby, who lives on Copeland Street, said she and her husband, Rufus Darby, were awake after watching the NBA Finals when they heard gunshots followed by screams and crying.

“I’ve lived here for 30 years, and I’ve never ever been afraid. But this time it felt like they were shooting in my house,’’ Bracey-Darby, 72, said late Saturday morning. “I thought I was going to die.’’

Earlier in the day, Bracey-Darby said she went outside to see if gunfire had hit her home, and learned that bullets had struck her Mercedes-Benz, which was parked out in front, shattering two windows and leaving a hole in the driver’s side door.

“There were so many gunshots that I had the taste of gunpowder in my mouth. That’s how close it was,’’ she said. “It really was horrible.’’

City Councilor Kim Janey, who also lives on Copeland Street, said she heard the gunfire from inside her home.

“As you can imagine, with four people shot, it’s a chaotic scene,’’ Janey said Saturday. “This is a dense neighborhood, so even for folks who were not outside, people heard this, and that is very traumatizing.’’

City trauma teams were activated, Janey said, and have reached out to the victims and their families. The teams are also planning to offer assistance to neighborhood residents, she said.

“After reporters leave our street, we are left here to pick up the pieces, we are left here to find some normalcy and peace of mind,’’ Janey said.

Earlier this year, she said, she held an annual Easter egg hunt at Little Scobie Playground, which drew hundreds of people.

“We are not defined by shootings. That’s not what defines us,’’ Janey said.

Copeland Street, however, has struggled with violence.

In April 2017, a 6-year-old boy was shot near 12-14 Copeland St. where he was visiting a relative’s house. He survived.

At the time of the shooting, police officials said the child’s father was the intended target, though the boy’s family disputed that.

Near the Burger King on Cummins Highway Saturday afternoon, there was no indication that a shooting had occurred just hours before. The victim was in critical condition early Saturday, but Evans said the man was expected to survive.

Scott Hill, 56, who was on Cummins Highway Saturday afternoon, said the neighborhood needs more police officers to control the violence.

“There’s no police presence,’’ he said. “Put more cops out here.’’

Globe correspondent Lucas Phillips and Danny McDonald of the Globe staff contributed to this report. Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi. John Hilliard can be reached at john.hilliard@globe.com.