Acquaintances of the Boston bombing suspect killed in a shoot-out with police Friday speculated Monday that he may have been involved with the murder of three Boston men in an unsolved case that dates to 2011.

Raphael Teken (photo credit: Facebook)

Raphael Teken (photo credit: Facebook)

At least two of the murdered men — Raphael Teken and Erik Weissman — were Jewish. (Friends of both Teken, 37, and Weissman, 31, maintain Facebook memorial pages in their honor.) The third victim in the September 2011 triple-homicide, Brendan Mess, was said by Tamerlan Tsarnaev’s acquaintances to have been his closest American friend.

The three men were found dead at Mess’s apartment in the Waltham suburb of Boston, having been stabbed in what was reported as a drug-related killing. The case remains open, and no suspects have ever been named, though investigators believed the killer knew his victims.

Local investigating authorities on Monday refused comment on any connection between the cases.

“At the time none of [us] would have thought it was Tam,” a man identified as Ray, who was said to have been friendly with both Tsarnaev and Mess, told the website Buzzfeed of the 2011 killings. (The site said it knew Ray’s full name, but had been asked by him not to publish it.) “It was just so emotional, and we thought we had someone else who had done it. Tam’s name wasn’t coming up at all.”

But since the Boston bombings, added Ray, ”a few of my friends, without even speaking about it beforehand, have all been thinking” that Tsarnaev could have been involved in the triple 2011 killings.

FBI photo of Boston bombing suspect Tamerlan Tsarnaev, who was killed on Friday, April 19 (photo credit: AP/FBI)

FBI photo of Boston bombing suspect Tamerlan Tsarnaev, who was killed on Friday, April 19. (photo credit: AP/FBI)

Mutual friends said they were surprised that Tsarnaev didn’t show up at his best friend Mess’s funeral, Buzzfeed reported, but now saw his absence as a clue.

“Tam wasn’t there at the memorial service, he wasn’t at the funeral, he wasn’t around at all,” Ray said. “And he was really close with Brendan.”

Ray said he’d had no further contact with Tsarnaev since the 2011 murders. “Those three guys all had their throats cut, and they had marijuana dumped all over their bodies,” Ray said. “It’s really gruesome how they were killed. It’s not something typical you’d see in Waltham. Not some home invasion gone wrong or something.”