The 2013 Boston Marathon bombings case is closed and a suspect is on death row, but there is still a lingering thread between the terrorist attack and gruesome murders that took place not too far away a year and a half earlier.
Mounting evidence appears to make a connection between a 2011 triple homicide and one of the bombers.
The ABC News Studios docuseries "The Murders Before the Marathon," which began streaming on Hulu on Sept. 5, follows the investigation by Boston-based journalist Susan Zalkind, who has spent years trying to get to the bottom of the possible connection between the bombings and the triple homicide.
Zalkind has interviewed dozens of witnesses, law enforcement sources and confidants and collected documents that have helped to paint a more accurate picture of the killings.
On the night of Sept. 11, 2011, Brendan Mess, Erik Weissman, and Raphael Teken met up to watch a football game in Mess's apartment in Waltham, Massachusetts. The next morning Mess's girlfriend found their bodies with their throats slit, nearly decapitated, and covered in marijuana and cash. Investigators said the three men, who were known to have sold marijuana within the community, were targeted; it was not a random crime.
According to the Middlesex District Attorney's office, the murders are still under investigation and remain unsolved
When she was home from college, Zalkind became friends with Weissman and followed the case in the news as the investigation continued.
While there was no breakthrough in the case, things changed following the April 15, 2013, Boston Marathon bombing. Three people were killed and hundreds were injured during the attack.
Tamerlan Tsarnaev, then 26, and his brother, Dzhokhar Tsarnaev, then 19, were identified as the prime suspects three days later and were hunted by the authorities. As word about the suspects spread and news reports included their photos, several people who knew the victims of the Waltham murders began to recognize the bombing suspects.
"I stood up and was like, 'Hey, that guy looks familiar.' I don't know how, I don't know why, I don't know from where, but that guy looks familiar," Ryan Dermitt, a friend of Brendan Mess, said.
Watch the ABC News Studios special “The Murders Before the Marathon” on Hulu.
Tamerlan Tsarnaev was an amateur boxer in Massachusetts and trained with Mess at the same boxing gym, according to people who were friends with both men.
"They were best friends. As a matter of fact, like shortly after Brendan's death, I went up to Tamerlan and said, 'I'm sorry for your loss. I know that was your best friend," Sean Gannon, who trained at the gym, said.
On April 19, Tamerlan Tsarnaev died following a shootout with police during which he was run over by his brother, who was attempting to flee in a stolen car. Dzhokhar Tsarnaev was arrested following the encounter.
Dzhokhar Tsarnaev was later convicted and sentenced to death for his role in the bombings. He is currently awaiting execution.
After the arrest, investigators began to look into the possibility that the elder Tsarnaev was involved in the Waltham murders. According to Zalkind, several of the victims' friends said they told police about Tamerlan Tsarnaev's connections with one of the murder victims, but Zalkind says she has found no records of the local authorities speaking with him during the initial investigation
The Middlesex district attorney's office said it couldn't initially comment because the Waltham murders is an open case.
On May 22, 2013, an FBI agent, two Massachusetts State Police officers and other law enforcement agents interviewed Ibragim Todashev in an Orlando apartment complex.
Todashev was also friends with Tamerlan Tsarnaev and trained at the same gym where he and Mess attended.
Initially after Todashev's death, what happened during the interview was unknown as federal investigators only released heavily redacted reports. But over the years more information has been released.
What is known is that sometime during the interview Todashev tried to attack one of the investigators, which prompted the FBI agent to open fire, killing him, according to an investigation by the Florida State Attorney's office.
The Waltham murders were discussed during the interview, according to the report, but there was very little shared publicly about the details, even though the conversation was allegedly recorded. Todashev allegedly implicated Tamerlan Tsarnaev in the 2011 murders, claiming the two were going to rob someone, according to reports. Todashev allegedly told investigators he did not know there was going to be a murder, according to reports.
Investigators have not officially confirmed those details.
Zalkind was able to obtain an unredacted document allegedly written by Todashev during the 2013 interview where he tells the story of a robbery that he and Tamerlan Tsarnaev committed in September 2011.
"He says he went to the apartment. Tamerlan had a gun. They went upstairs. And they taped three men up. And that's when he stopped writing," Zalkind said.
There is no mention of the killings in the written statement.
Zalkind was able recently to get confirmation from the Middlesex County district attorney's office through a public information request that Tamerlan Tsarnaev and Ibragim Todashev are persons of interest in the Waltham murder investigation.
"They say, 'The office continues to investigate the potential involvement of an additional undisclosed person or persons in connection with these homicides.' They say, 'As recently as November 2021, we have identified new potential sources of physical evidence.' And they say, 'in the past year, we have interviewed a material witness," she said.
Zalkind, who is writing a book on the Waltham murders, said there are still questions left unanswered.