The FBI is reviewing the death of Ibragim Todashev, the Chechen immigrant killed last week in Orlando, Fla., during a standoff with an FBI agent and a Massachusetts state police officer. The incident that has sparked accusations from Todashev's family that the killing was unjustified.

Thursday, Todashev's father held a news conference in Moscow and asserted that his son's death amounted to an "execution-style" killing at the hands of U.S. agents and accused the FBI of shooting his son at least six times, once in the back of his head. Todashev's wife, Reni Manukyan, also spoke out this week, questioning the FBI's explanation of the apparent shot in the head and calling for an independent review of the incident.

"It's the way how they are saying he was protecting himself, that it was self-defense from the FBI agent," she said. "I don't think it is self-defense, you would not have shot him on the top of his head. It just cannot be true." (...)

"The Massachusetts state trooper never even got his gun out because of the tight space and the crossfire," Miller added, "It would have been too dangerous."

Authorities have confirmed to CBS News that the FBI agent fired six times.

The shooting review board -- which will have representatives from the Department of Justice, and from the FBI's firearms and tactical operations teams -- will comb through that sequence of events and interview relevant witnesses. "The FBI lab will do a separate probe to see if the forensics tell the same story before it goes to the review board," Miller said Friday on "CBS This Morning."

Addressing the questions regarding reasonable use of force in the standoff that led to Todashev's death, Miller said, "I was trained in the FBI policy on use of force ... the standard is if you believe you or your partner or somebody with you is going to be the victim of either serious bodily harm or possibly death, you have the right to use deadly physical force."