A former sheriff’s deputy in Florida was charged with manslaughter on Friday, more than three months after he fatally shot a U.S. Air Force senior airman who answered the door to his apartment holding a gun that was pointed to the ground, prosecutors said.

A warrant was issued charging Eddie Duran, a former deputy with the Okaloosa County Sheriff’s Office, with one count of manslaughter with a firearm, State Attorney Ginger Bowden Madden said in a news release. He had not been arrested as of Friday afternoon.

The charge against Mr. Duran, 38, who was fired in late May after the sheriff’s office conducted an internal investigation into the fatal shooting of the senior airman, Roger Fortson, 23, marked an unusual instance in which a law enforcement officer in Florida’s panhandle faced a felony charge in connection with a shooting, a local prosecutor said.

If convicted of the charge, Mr. Duran could face a maximum sentence of 30 years in prison.

Efforts to reach Mr. Duran on Friday were unsuccessful, and phone and email messages to a lawyer for Mr. Duran were not immediately returned.

The authorities said that Mr. Duran had been directed to Airman Fortson’s apartment in Fort Walton Beach in response to a domestic disturbance report that turned out to be false, The Associated Press reported.

Body camera footage showed that Mr. Duran first knocked on Airman Fortson’s door on May 3 without identifying himself.

He then knocked again, announced himself and stepped away from the door. Seconds later, the deputy shifted to the other side of the door, knocked and announced himself again. Airman Fortson, who was holding a gun in his right hand that was pointed to the ground, opened the door and was immediately shot.

After Airman Fortson collapsed, Mr. Duran yelled, “Drop the gun!”

Ben Crump, the civil rights lawyer who represents Airman Fortson’s family, called the decision to charge Mr. Duran the “first step towards justice.”

“Nothing can ever bring Roger back, and our fight is far from over, but we are hopeful that this arrest and these charges will result in real justice for the Fortson family,” Mr. Crump said in a statement.

The shooting death of Airman Fortson drew widespread attention.

In May, Mr. Crump, who represented the family of George Floyd, also released separate video footage from the day Airman Fortson was shot that he said Airman Fortson’s girlfriend had recorded while on FaceTime with the airman.

The footage begins moments after Airman Fortson was shot. He is heard heaving and says, “I can’t breathe.”

Lawyers for Airman Fortson’s family have not disputed that he was armed but said that he had every right to be as a legal gun owner in his own home.

The Okaloosa County Sheriff’s Office said in a statement on Friday that it had been “fully accountable and transparent” in the case and noted that it had provided public statements and made body camera footage of the deadly encounter available.

“We stand by our decision to terminate Mr. Duran as a result of the administrative internal affairs investigation that found his use of force was not objectively reasonable,” the sheriff’s office said.

Initially, the sheriff’s office had said that Mr. Duran had “reacted in self-defense.”

In an interview on Friday, Greg Marcille, assistant state attorney of the First Judicial Circuit of Florida, said that it was “unusual for law enforcement to be charged with a case that involved a death.”

“We’ve investigated other instances involving law enforcement shootings,” he said, “but this is one of the few times that an officer has been charged.”

Kirsten Noyes contributed research.