PUNTA GORDA, Fla. — A police ‘‘shoot/don’t shoot’’ demonstration in Florida went shockingly awry when an officer shot and killed a 73-year-old former librarian with what police said was real ammunition used by mistake at an event designed to bring police and the public together.

Authorities didn’t immediately say how a gun with a live round came to be used at Tuesday evening’s demonstration, noting blank rounds are typically used in such classes.

A Punta Gorda police spokesman identified the officer as Lee Coel and said Coel has worked for the department since 2014.

She said Coel frequently gave department presentations and tours, ‘‘specifically role-playing in these shoot/don’t shoot scenarios.’’

Coel has been placed on administrative leave, and the Florida Department of Law Enforcement is investigating.

‘‘The officer involved is grief-stricken,’’ Police Chief Tom Lewis said at a news conference Wednesday. “We’ve got officers assigned to him to make sure he’s psychologically stable.’’

Mary Knowlton, a community volunteer, was shot after being randomly selected to take part in the role-playing scenario illustrating the split-second decisions an officer must make about firing. It was part of a popular citizens academy attended by 35 people, including her 75-year-old husband.

Her son, Steve, said his father was devastated.

The younger Knowlton said in an interview Wednesday at his parent’s home that, on his mother’s behalf, he was forgiving Coel.

‘‘There’s too much hate in this world, in America, we always feel like we need revenge and it doesn’t solve anything,’’ he said. ‘‘I obviously can’t say it’s easy to forgive, but it needs to be done. She’s watching me now.’’

Police Lieutenant Katie Heck said officers in such demonstrations normally use ‘‘simunition guns,’’ which are real-looking weapons that fire a nonlethal projectile with reduced force.

The class, put on by the Chamber of Commerce and the Punta Gorda police station, was one lesson during a weeks-long curriculum.