MOSCOW-The father of a Chechen man who was friends with one of the alleged Boston Marathon bombers claims his son was shot "execution style" by the FBI last week.

"I want justice and an investigation in accordance with American laws to punish those who are guilty," Abdul-Baki Todashev said. "They were not FBI employees, but bandits."

The deceased man, 27 year-old Ibragim Todashev, was shot and killed by FBI investigators who were interrogating him about whether he had any role in, or had any advance knowledge of, last month's Boston Marathon bombing. They also questioned him about his role in an unsolved triple murder in 2011. Todashev was a friend of Tamerlan Tsarnaev, one of the suspects in the Boston attack.

Todashev was shot seven times, including once to the head, according to his father. He displayed graphic photos, taken by friends who claimed the body from an Orlando area morgue, as evidence. The authenticity of the photos could not be verified, but they show several bullet holes in the body, including one to the head.

"To make sure that he was dead," the father said, speaking in Russian.

At a press conference in Moscow, where he is applying for a visa to travel to the United States to collect the body, Abdul-Baki Todashev questioned why his son had been shot so many times even though he was said to be unarmed.

"They could have simply grabbed my son or, in the worst case, they could have wounded him," he said, noting that the FBI's story has been evolving.

"They simply killed him as they wanted and my opinion is that they wanted to get rid of him to shut him up," he added.

Initially, the FBI said that the agents felt endangered after Todashev attacked them with a knife and they fired on him in self defense. This week, however, officials said he lunged, possibly for one of the agent's guns or a sword that was in the room, but was unarmed when he was killed. The press conference was scheduled before the latest FBI revelation.

Abdul-Baki Todashev said his son was killed during his third interrogation by law enforcement. During the first, he said, the younger Todashev was questioned about his role and knowledge of the Boston bombing. During the second interrogation, they began to ask him about the triple murder in Waltham, Mass., he said. Officials claim Todashev was in the process of confessing to the murders when he threatened the agents.

The father denied his son was involved in the Boston bombing, saying Todashev only knew Tamerlan Tsarnaev because they boxed at the same gym in Boston.

"They were just acquaintances, not close friends," the father said. He denied his son had any ties to militants or extreme religious views.

The father cast doubt on the FBI's claims that his son was about to confess to a role in the triple murder, noting that his son had received a green card just a few months ago and would not have been able to do so if there was any suspicion about him.

"I know him so well. I know what he can do and what he can't," the father said.

He questioned why a friend, who was also interviewed that night, was asked to leave when they began to interview Todashev. He also wondered why no video or audio evidence has been made public to corroborate the FBI's version of events.