A former police officer who shot and killed an unarmed black man in Tulsa, Okla., in 2016 will not face federal civil rights charges, the Justice Department said Friday, noting that it had found insufficient evidence to prove she had willfully used unreasonable force when she killed him.

Betty Shelby, a white officer who worked for the Tulsa Police Department at the time, said she shot Terence Crutcher in September 2016 in self-defense because she thought he was reaching into his car for what might have been a weapon. Video of the episode showed Mr. Crutcher holding his hands above his head when he was shot.

On Friday, the Justice Department said it had found insufficient evidence to prove that her use of force against Mr. Crutcher was “objectively unreasonable” under the definition set by the United States Supreme Court.

“Any allegation of law enforcement misconduct and willful deprivation of civil rights is taken seriously,” R. Trent Shores, the United States attorney for the Northern District of Oklahoma, said in a statement. “However, the evidence in this case did not support pursuing criminal prosecution. Moving forward, I hope that citizens and law enforcement will continue to work together to better our community.”