Because he attacked them...
That's a good point you bring up.
However, I think it's important to consider that first off, that is not yet accurate information. The FBI is still reviewing the case. Although with their perfect track record of internal investigations on FBI agents killing people in these situations, I think we can bet our money on the outcome being in favor of the FBI being justified.
Either way, there's discrepancies on what happened that day, so we can't really say it who did what.
Again from Wikipedia...
On May 22, 2013, law enforcement officers, including an FBI
special agent from the
Boston field office, and two
Massachusetts State Police (MSP) troopers, interviewed Ibragim Todashev for approximately eight hours at his apartment in
Orlando, Florida. They questioned him regarding the 2011 Waltham murders and his connections to the Boston bombings suspect Tamerlan Tsarnaev.
[2][16] Both Todashev and Tsarnaev had trained at the Wai Kru gym and lived close to each other in
Cambridge, Massachusetts.
[9] The investigators later said that Todashev implicated both himself and Tamerlan Tsarnaev in the murders during the questioning. They reported that Todashev was beginning to write a formal statement when he asked to take a break, and then suddenly attacked the FBI agent.
[2][16] Todashev was shot multiple times and killed.
[2][17][18]
Officials initially claimed that Todashev picked up a knife or attempted to grab a samurai sword, but later said that it was unclear whether this was the case; one source said it was "a knife or a pipe or something". A number of later reports said that he was unarmed.
[17][18][19][20] Some earlier accounts implied that the FBI agent was alone with Todashev at the time of the shooting.
[18] Following Todashev's death, his father showed photographs to reporters in Moscow that he said demonstrated his son had been shot at point-blank range in the head.
[21] According to the account of an unnamed law enforcement official, Todashev knocked the interrogating agent to the ground with a table, and then lunged at him with a metal pole, or possibly a broomstick.
[22] In this account there was one detective in the room—who did not fire—besides the FBI agent.
[22] The agent sustained minor injuries requiring
stitches. An account given by former FBI deputy director
John Miller states that an MSP trooper "noticed that Todashev was getting more and more agitated. Rather than alert the agent and tip off Todashev that they sensed something was about to happened, [the trooper]
texted the agent and [wrote], 'Be careful, I think this guy is becoming more agitated'. As the agent looked down at that text, that's when the table went over, Todashev came over the table and picked up apparently a metal broom handle or some object like that [...] and charged the agent. The agent [w]as knocked back, came up with his gun, fired two or three times. Todashev came back at him and he fired more times." Authorities have confirmed that the agent fired six times.
[23]
Todashev's body was flown to Russia on June 20 by his American widow and his father,
[24] and was buried in a Muslim cemetery in Grozny on June 29.
[25] The FBI established a post-shooting incident-review team to investigate the shooting.
[16] On July 16, the release of Todashev's autopsy report, completed by a Florida medical examiner's office, was blocked by the FBI because the "case was still under active investigation."
[26]
Allegations of civil rights violations and excessive use of force
On May 29, the
Council on American–Islamic Relations (CAIR), an American Islamic civil liberties group, held a news conference in Orlando at which it presented photographs of Todashev's body which it said showed that he was shot seven times, once in the head.
[27] CAIR asked the
Department of Justice for an investigation separate from the FBI investigation into the shooting to determine whether the FBI violated Todashev's
civil rights.
[28] The FBI immediately responded with releasing a statement saying: "The FBI takes very seriously any shooting incidents involving our agents, and as such, we have an effective, time-tested process for addressing them internally. The review process is thorough and objective and conducted as expeditiously as possible under the circumstances."
[29]
On June 5, the
American Civil Liberties Union (ACLU) has also called for an independent investigation into the shooting. Michael German, a former FBI agent and ACLU's counsel on national security, immigration and privacy,
[30] said: "What became concerning is that different stories... were coming out. They need to correct the record—both for the protection of the people in the community and for the protection of the law enforcement officers."
[29][31] A Department of Justice spokesman said that they are going to determine whether their
Civil Rights Division investigation of the killing is warranted.
[32]