Former associates of slain Boston Marathon bombing suspect Tamarlan Tsarnaev now believe he may have been involved in a 2011 triple murder that claimed the life of his closest American friend, Brendan Mess.

“At the time none of would have thought it was Tam. 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,” said one of their mutual friends, who asked to be identified by his first name, Ray.

Now “a few of my friends, without even speaking about it beforehand, have all been thinking” that Tsarnaev could have been connected to the 2011 murder, he said. Ray and Tsarnaev were both part of a social circle centered on the gym at which Tsarnaev trained and on a Boston hip-hop group called FlyRidaz, whose members this week expressed shock at having known the suspected killer.

Ray gave BuzzFeed his full name but asked that it not be used because, he said, he is concerned for his safety. Other friends were more reticent about speaking with reporters. But some have been reflecting on their knowledge of Tsarnaev on social media.

“This is so crazy. Lots of us knew the older suspect. UNREAL AND TERRIBLE,” a former friend wrote.

“I just put together what this meant and I’m buggin the fuck out,” responded another.

The 2011 murder has returned abruptly to the forefront of their minds.

The owner of the Wai Kru Mixed Martial Arts in Allston, John Allan, told reporters that Tsarnaev described Mess to him as his “best friend.”

So the Cambridge crew were surprised in the fall of 2011 that Tsarnaev didn’t show up at his best friend’s funeral. Now they see it as a clue.

More: ‘Boston Bomber’s’ Former Friends Suspect Him in Triple Murder