Abdulbaki Todashev spoke about his son, Ibragim Todashev, on August 13 in Tampa, Florida, after traveling from Chechnya.
"I hope and pray that no mother and no father will ever have to endure or go through what I'm going through right now," he said. "My son was a very good boy and he is innocent and he was simply killed."
Abdulbaki Todashev said he was now seeking justice in the United States over the death of his son.
Lawyers for the father indicated a civil suit against the FBI was being considered.
Ibragim Todashev, 27, was shot dead on May 22 in Orlando, Florida, while being questioned by U.S. agents about his links to slain bombings suspect Tamerlan Tsarnaev, a fellow ethnic Chechen.
The FBI has said an agent opened fire after Todashev, who was unarmed, suddenly attacked an agent.
Officials initially said Todashev had lunged at an agent with a knife. Later, officials said it was unclear what happened.
An investigation of the incident is being led by the FBI.
Abdulbaki Todashev has raised doubts about the FBI’s account. He says his son was unarmed and was shot seven times.
Lawyers for the father said Ibragim Todashev was recovering from a knee injury at the time of the shooting and would have had difficulty attacking agents.
The FBI declined comment, citing the ongoing investigation.
Ibragim Todashev, who had trained as a mixed-martial-arts fighter, was an acquaintance of bombings suspect Tamerlan Tsarnaev and had worked out at the same gym as Tsarnaev in Boston before moving to Florida.
Tamerlan Tsarnaev was killed in a shoot-out with police days after the April 15 Marathon bombings, which killed three people and injured more than 260.
In another development, two college students from Kazakhstan have pleaded not guilty to charges that they conspired to obstruct the investigation of the bombings.
Dias Kadyrbaev and Azamat Tazhayakov, both 19, appeared in a federal court in Boston on August 13 wearing orange prison jumpsuits.
If convicted of allegations they conspired to impede the investigation, they could face more than 20 years in prison.
Authorities accuse the pair of removing, destroying, and concealing some of the belongings -- including a laptop and backpack -- of the second bombings suspect, Dzhokhar Tsarnaev, with whom they were friends at the University of Massachusetts.
Dzhokhar Tsarnaev, the younger brother of Tamerlan Tsarnaev, has pleaded not guilty to charges of carrying out the bombings. He is facing trial.