The sound of ambulances and police cars roaring are not uncommon in the Melville-Park neighborhood. But, neighbors say, the emergency vehicles are usually racing to someplace else in Dorchester.

But on Dec. 13, 2005, they all converged on Bourneside Street - a short side-street opposite Town Field - and launched an investigation into the murders of four young men, three of them members of a nascent local rap group, Graveside.

The case came to an apparent conclusion last week, when accused killer - 21-year-old Calvin Carnes - was convicted and sentenced to four consecutive life sentences, one for each young man shot to death in the house's basement: 20-year-old Jason Bachiller, 21-year-old Edwin Duncan, 19-year-old Chris Vieira - who were members of the rap group - and their friend, 22-year-old Jihad Chankhour.

The quadruple homicide brought the year's total for Boston's murders to 71, a 10-year high for the city. Thinking back to that night, Lee Robinson remembers hearing her neighbors screaming.

"I never want to hear that again," recalled Robinson, who lives nearby on Wellesley Park. "These were basically good kids."

"People feel like they lost some neighbors," added Peter Sasso, who lives in Melville Park. "The neighborhood is relatively safe for a city neighborhood."

Neighbors say that the fact that the Bourneside Street home was purchased soon after the murders is evidence of the neighborhood's continued vitality. Darnella Phillips, Duncan's mother and a retired MBTA operator, has moved to Georgia. The other victims were from Wakefield.

Many neighbors also felt justice was served last week with the conviction of Carnes. In a trial often overshadowed by the Middlesex County case of a British man accused of killing his wife and child, Suffolk County prosecutors charged that Carnes emptied 13 rounds into the four young men. The motive, prosecutors argued, was robbery. Carnes coveted three firearms taken from the Graveside members. The trial ran for three weeks and saw 60 witnesses take the stand.

Spurred by a "spark of evil," as First District Attorney Josh Wall told the jury, Carnes shot the four in the back again and again with Vieira's unregistered Glock 9mm in an attempt to grab the gun and two others - a Mossberg 12-gauge shotgun and a rifle similar to an AK-47.

Robert Turner, Carnes's best friend, is serving 13 years in state prison for helping Carnes get away, having pleaded guilty to all charges.

Lacking a clear focus on potential suspects in the investigation, police officers say it was a phone call from a person who knew both one of the victims and one of the defendants three days after the murders that lead them to Carnes.

"It was her information that led us to get subpoenas for telephone records of those defendants," says Boston Police Det. Juan Torres. "It all started with a single phone call."

Police also found Vieira's car, with the keys still in the ignition, on a Dorchester street near the home of one of Turner's relatives.

Police interviewed Carnes twice, once in his home on Dec. 22 and again in February at Boston Police headquarters. Both times he gave different accounts of where he was at the time of the crime.

In the first interview, according to records obtained from Suffolk District Attorney Dan Conley's office, Carnes said he received a phone call from Vieira to come to the basement, which served as a makeshift studio for the rap group, Graveside. Carnes told him he would come, but a half-hour later he got a phone call from a girl who wanted to hook up with him, he told police.

The next time he heard anything about Graveside, it was the next day, he said.

In the second interview, Carnes said he was with Turner when he saw the girl. They and others hung out on the porch and smoked marijuana, he said. They walked her dog, staying in the area for several hours, with Carnes returning home around 11:30 p.m.

"Ultimately, those people didn't alibi him," Torres says.

Carnes and Turner were arrested in May 2006, in the middle of grand jury proceedings into the case.

Carnes gave another account on when he took the stand at the trial, saying he was selling marijuana on Florida Street, which was contradicted by a prosecution witness.

"He'd be the only person who'd have a reason and lie," Torres says.

Carnes's attorney, Shannon Frison, disagrees and plans on appealing the case to the state's highest court, the Supreme Judicial Court.

The differing alibis did have an impact on the jury, Frison admitted. But when Carnes took the stand, he was telling the truth, she said.

"We wouldn't have presented that alibi if it wasn't true," she said.

He was emotional when he was being interviewed by police, who didn't tell him either time that he was a suspect, she said.

Frison also criticized the trial's process, noting that three jurors were dismissed and alternates were seated in their place.

Several times, the jury reported being deadlocked 11 to 1, she said. "The judge would not accept that they were deadlocked," she said.

A spokesman for District Attorney Dan Conley's office, Jake Wark, said the judge said in open court that the jurors were switched out for personal reasons and the move was unrelated to their views.

Frison has also noted that the guns prosecutors say Carnes professed an interest in were found on three other people who have no connection to Carnes.

According to police, the Glock was recovered in a search for a person who was wanted on gun trafficking charges in federal district court. The assault rifle was recovered after undercover police officer bought it off two people.

The shotgun has not been recovered.

At the end of the trial, first assistant district attorney Wall played for the jury the 911 call Darnella Phillips made after discovering her son Edwin Duncan and his four friends murdered. It was filled her screams.

"The killer is in this courtroom, and he's right in front of you," Wall said.