The party in the Roxbury apartment complex had been going on for several hours when at least one gunman walked through the door and began firing, according to two law enforcement officials briefed on the investigation.
Two men and a woman, all in their 20s, were killed Saturday morning at the party on Intervale Street, in a section of the city that police consider a hot spot for violent crime and gang activity.
Police identified the victims as Ana Cruz, 22, Felix Garcia, 22, and Brian Tirado, 23. All three lived in Dorchester.
Their deaths brought the number of homicides in Boston this year to 26, three more than at the same time last year, police said. No arrests have been made in Saturday’s shooting, and police have not described a motive.
Outside the apartment complex where Garcia lived, less than a half a mile from where he was killed, several people who identified themselves as his siblings sat on the doorstep. Some stared ahead silently.
A young woman who said she was Garcia’s sister, but did not give her name, said he had not spoken of having problems with anyone.
“He just finished school, had a brand new job,” she said.
‘If there is a party out there, I want it shut down. I don’t want any excuses. Shut it down.’
On the Thursday before the incident, Mayor Thomas M. Menino and Boston Police command staff met to discuss a recent increase in shootings.
Menino said that at the meeting, he called on police to respond immediately to any house party over the weekend that drew complaints.
“My directive was, use the laws we have on the books, use any tool you have,” the mayor said, describing the meeting. “If there is a party out there, I want it shut down. I don’t want any excuses. Shut it down.”
Police spokeswoman Cheryl Fiandaca said no one had called to complain about the Intervale Street party before the shootings. Boston police and Suffolk prosecutors said they need the public’s help to solve the killings.
“The investigation remains very active,” said Jake Wark, spokesman for Suffolk District Attorney Daniel F. Conley. “Anyone with information, no matter how peripheral it might seem, is urged to share that knowledge with investigators.”
Parties in sections of the city known for shootings and other violence are particularly worrisome to police, especially during the summer. Drunken arguments can lead to fights that can end in fatalities. They can also draw rivals to the same place and spark a violent confrontation.
The circumstances of Saturday’s shootings remain unclear. Neighbors interviewed Monday said the music had been loud starting Friday afternoon, but none of them were concerned enough to call police.
The victims had been at the party “having a good time,” said a man leaving the complex on Intervale Street, who declined to give his name.
Many residents of the complex said they did not hear the gunshots; they learned that something was wrong only when they heard screaming from the street.
Neighbors said they saw at least six people run from the back of the complex and through an alley to cars that were parked in front of the building.
A resident who asked not to be identified because he feared for his safety said he heard one man yell to another: “Come on! Get in the car. Let’s go.”
The resident said he saw several cars speed away, but was unable to recall the make and model of the vehicles. Police have said they are looking for a maroon or red older-looking Mercury vehicle.
Menino said he is worried about recent shootings in which women have been injured or killed. Last Tuesday, an unknown assailant fired at a couple sitting in their car with their 4-year-old daughter in the back. Only the man was injured. That shooting occurred one day after a gunman shot at another couple whose 5-month-old daughter was in the back seat. The child was unharmed, but the man and woman were shot; they are expected to survive their wounds.
“We have to educate the young women out there about the dangers of some in the social life, who they hang out with,” Menino said.Travis Anderson of the Globe staff contributed to this report. Maria Cramer can be reached at email@example.com. Follow her on Twitter at GlobeMCramer.