Robert Turner, 21, received a 13-year prison term for being an accessory after the fact to the 2005 killings and for unlawful possession of three firearms, including the gun used in the killings, the Boston Globe reported. He has not agreed to testify for the prosecution.
"My actions were cowardice and heartless and also selfish," Turner said Wednesday, reading a handwritten statement. "I was raised to be strong, no matter what the situation was. ... My actions were wrong."
Calvin Carnes Jr., the alleged shooter, is scheduled to go on trial in May.
The victims were identified as Edwin Duncan, 21, Jason Bachiller, 20, Christopher Vieira, 19, and Jihad Chankhour, 22. Three of the young men were in a rap group that used the name Graveside.
During the hearing, Darnella Phillips, Duncan's mother, said she could not forget that Turner and Carnes had come into her home as guests and into her son's studio.
"To come into our home and take their lives -- I will never get over that," she said.