(ABC News) -- The man shot dead by an FBI agent in Orlando, Florida early today was "about to sign a statement" admitting to a role, along with Boston Marathon bombing suspect Tamerlan Tsarnaev, in an unsolved triple murder in Massachusetts in 2011, two people with direct knowledge of the case told ABC News.
Ibragim Todashev "just went crazy," and pulled a knife during his interview with the FBI, said state and federal law enforcement officials briefed on the latest strange twist in the investigation of the Boston Marathon bombing.
One official said an FBI agent was stabbed several times, although his injuries were described by the FBI as "non-life threatening."
FBI agents and Massachusetts state police began to question Todashev after his name and phone number were recovered from the phone of the dead bombing suspect. Tamerlan Tsarnaev was killed in a shootout with police days after he and his younger brother Dzhokhar allegedly planted two bombs near the finish line at the Boston Marathon April 15, killing three and injuring more than 260 others. Dzhokhar was later captured and is in custody.
Todashev and Tamerlan Tsarnaev both fought mixed martial arts in the name of Boston's Wai Kru gym, where one of the 2011 triple murder victims, Brendan Mess, also trained, according to a former fighter there and law enforcement officials.
According to officials, Todashev was initially being questioned about any role in the marathon bombing when it emerged he had connections to the gruesome murder. There is no indication Todashev was tied to the bombing, sources familiar with the case said.
In the wake of the bombing, detectives developed DNA evidence linking both Tamerlan Tsarnaev and his younger brother Dzhokhar to the triple murder scene.
The three men who were killed had their throats slit and their bodies were left with cash and marijuana placed on top of them. The murder took place on September 11, 2011, the ten year anniversary of the al Qaeda terror attacks on New York and Washington.
Also killed with Mess were Raffael Teken and Eric Weissman. A spokesperson for the Middlesex County district attorney, which is handling the triple murder investigation, declined to make any official statement.
According to a recent Florida police report, Todashev was arrested May 4 and booked with aggravated battery for allegedly fighting with a father and son over a parking space in a mall parking lot in Kissimmee, Fla. Todashev had told police he fought in self-defense as the son "came at him swinging" after Todashev pushed the father.
Neither father nor son wanted to press charges in relation to the altercation, the report said. The report lists Todashev's place of birth as Russia.
Freelance writer Michele McPhee is a Boston-based reporter and frequent contributor to ABC News.