In the ensuing investigation of the marathon bombings, authorities also questioned Todashev, who had moved to Florida.
While being questioned in his home May 22 by an FBI agent and Massachusetts state police officers, Todashev admitted he played a direct role in the Waltham killings and implicated Tamerlan Tsarnaev as well, a federal law enforcement source told CNN at the time.
Todashev told investigators the men were killed during a drug ripoff because he and Tsarnaev were afraid they would be able to identify them and tell police what happened, according to a law enforcement source.
A U.S. government official briefed on the investigation said that while being questioned, Todashev suddenly knocked over a table, brandished "a long-handled object" and lunged at the FBI agent, who shot and killed him. The shooting remains under investigation.
Middlesex County District Attorney Marian Ryan said after Todashev's death that the Waltham killings remain an "open and active" case, and that police and prosecutors "have conducted a thorough, far-reaching investigation."
"This investigation has not concluded and is by no means closed," Ryan said.
Now some of those who knew Weissman, Teken and Mess are questioning whether Tsarnaev should have been under scrutiny long before the marathon attack.
Looking back at the young man's attitude following the Waltham murders, Allan wonders whether a big clue was missed.
"Retrospectively, maybe there was something behind that," he said.