MIAMI - A civil rights group for Muslims have said it will sue the Federal Bureau of Investigation over the 2013 shooting death of a friend of a Boston Marathon bombings suspect.

Ibragim Todashev, 27, was killed after a violent altercation with investigators following lengthy questioning at his apartment in Orlando, Florida in May 2013.

The FBI said Todashev had pulled a knife on investigators and tried to grab an agent’s gun following questioning on his role in the Boston bombings.

But the Florida chapter of the Council on American-Islamic Relations (CAIR) disputes the version of events.

“Around midnight, after five hours of interrogation, (Agent Aaron) McFarlane shot Todashev. Seven times. Todashev was unarmed with any gun, knife, explosive, or other deadly weapon,” CAIR said in a statement.

“Todashev did not pose a threat of serious bodily harm to McFarlane or any other person. No viable justification has been offered to account for McFarlane’s shooting and killing Todashev.”

CAIR said it had sent a formal notice to the FBI, the first step in a civil rights lawsuit against the national police agency.

“We are seeking answers and justice for someone who was shot seven times by an FBI agent in his own home after hours of interrogation,” said Thania Diaz Clevenger, the civil rights director for CAIR Florida.

The FBI said it could not comment on pending litigation, but pointed to reports last year by the Department of Justice and the Florida State Attorney’s Office, both of which cleared the agency.

Police have said Todashev, a friend of slain Boston bombings suspect Tamerlan Tsarnaev, had confessed to his and Tsarnaev’s involvement in a September 11, 2011 triple murder before he was shot.

Todashev had been questioned several times in the aftermath of the April 15, 2013 bomb attack on the Boston Marathon allegedly carried out by Tsarnaev and his brother, Dzhokhar Tsarnaev, which left three people dead and 264 injured.

Dzhokhar Tsarnaev’s trial is due to start Wednesday.