(CNN) - Ibragim Todashev, shot dead early Wednesday by the FBI in Florida, had been acquainted with Boston Marathon bombing suspect Tamerlan Tsarnaev at a mixed martial arts center near Boston, according to a source briefed on the bombing investigation.
Todashev had Tsarnaev's phone number in his cell phone, the source said.
Both were members of the mixed martial arts forum Sherdog.com, along with Russian-Canadian boxer-turned-jihadist William Plotnikov, the source said.
Last month, CNN reported that Plotnikov and six others died in a July 2012 firefight with Russian forces in the southwestern republic of Dagestan, while Tsarnaev was visiting the region, according to a source briefed on the investigation.
An FBI agent fatally shot Todashev in Orlando as authorities investigated whether Todashev was connected to the Boston Marathon bombings, a U.S. law enforcement official with direct knowledge of the Boston case told CNN.
Todashev, 27, also knew Dzhokhar Tsarnaev, who is also a suspect in the April 15 bombings, the official said. Dzhokhar Tsarnaev, injured and captured after a manhunt, is being held by authorities. Tamerlan Tsarnaev, his older brother, was killed in a shootout with police shortly after the bombings.
The agent shot in self-defense in the incident, which occurred at Todashev's house, the law enforcement source said.