BOSTON (AP) – Four men were shot to death Tuesday night inside a basement that neighbors said had been set up as a music studio, police said.

Boston Police Superintendent Bobbie Johnson said officers arrived at the house in the city’s Dorchester section to find three men dead. The fourth died later at Boston Medical Center.

The dead were described as in their late teens and early 20s.

Johnson said witnesses told police they saw a heavyset person fleeing the scene. No arrest had been made.

Police said the people involved appeared to know each other, but Johnson would not comment further on any possible suspects.

The killings came in a neighborhood that had been considered relatively safe, as Boston struggles with a spiraling murder rate.

Late last month, the city recorded its 66th homicide this year, surpassing the total for all of last year and equaling a 10-year high.

The Rev. Jeffrey Brown, co-founder of an anti-violence coalition who lives nearby, said he was shocked by the crime.

“The level of violence that we’ve seen in other parts of the neighborhood doesn’t exist in this neighborhood,” he said. “For something like this to happen, it really crosses the line.”

Johnson also said police had not had any problems at the address in the past.

“The neighbors have seen the kids go in and out, but they have not had the need to call police to intervene,” said Johnson.

The house at 43 Bourneside Street is a three-decker typical of the thousands of three-family homes that dot Boston’s neighborhoods. Johnson said ballistic evidence was found at the scene.

“The incident happened in the basement, inside, and even if we had a 100 cops on the beat it probably wouldn’t have prevented this type of crime,” Johnson said.

The spate of killings prompted a recent sweep by dozens of Boston police officers working overtime shifts in search of suspects wanted on charges involving violence and guns. U.S. Attorney Michael J. Sullivan said last week that his office will increase federal prosecutions of suspects involved in gun and gang violence in Boston. He also said law enforcement hasn’t done enough to intercept potential offenders before they commit crimes.

Brown said he and other ministers have been trying to take steps to lower the level of violence in the city.

“The ministers have banded together to do all we can to alert the neighborhood that it is our responsibility to put a stop to all of this,” he said. “We have to rise up now and fight this culture of intimidation and indifference that breeds this kind of violence.”