The father of Ibragim Todashev, the 27-year-old friend of Boston bombing suspect Tamerlan Tsarnaev who was killed during an FBI interrogation in May, announced on Monday that he will sue the FBI for the death of his son.

Ibragim Todashev, the man fatally shot last week by an FBI agent during an interview about Boston Bombing suspect Tamerlan Tsarnaev, was unarmed. Initial reports said that Todashev had attacked the agent with “a knife or a pipe or something.”