A Florida police officer who accidentally shot to death a retired Twin Cities school librarian during a role-playing exercise last summer has been charged with a felony, and the police chief was charged with a lesser offense and put on leave from his post, authorities announced.

Punta Gorda officer Lee Coel was charged Wednesday in Charlotte County with felony manslaughter for firing the shot that killed 73-year-old Mary Knowlton during the academy’s “shoot/don’t shoot” exercise. Coel was booked into jail and then released Wednesday.

Police Chief Tom Lewis has been charged with culpable negligence, a misdemeanor. Lewis was placed on paid administrative leave with pay “while we sort this out” with “a full internal affairs investigation into the entire situation,” City Manager Howard Kunik said Thursday.

If convicted, the officer could receive a long prison sentence, while the chief would face up to 60 days in jail. Coel has been on administrative leave since the shooting and remains off the force as the criminal case and a city investigation go forward.

In announcing the filing of the charges, State’s Attorney Steven Russell said members of his office “met with Mary’s husband, and we have advised his counsel that we are moving forward on this case. The Knowlton family is dealing with a tremendous loss, and we wanted to make sure they are informed.” The Knowlton family later declined to comment about the charges.

Jerry Berry, attorney for the officer, told reporters that he and his client “were surprised” by the decision to charge and said that Coel “did not know there was live ammunition in that gun. He’s devastated.”

The attorney added that “once we can present our side of the case and additional facts that [prosecutors] might not know about, we’re comfortable that the case will be dismissed or a jury will find him not guilty.”

Mary and Gary Knowlton, formerly of Prior Lake, were among 35 Citizens Academy participants at police headquarters, where Knowlton and another person were chosen for the exercise designed to re-create a lethal-force scenario involving police.

Mary Knowlton assumed the role of a police officer, while Coel was decked out as a “bad guy” in a hoodie and mask with a revolver.

An investigation determined that live ammunition had been mistakenly mixed in with blanks.

In October, the family agreed to a settlement exceeding $2 million with Punta Gorda, the city where she had retired.

As part of the proposed settlement, the city “denies violating any laws or breaching of duties” in connection with the death, the agreement read. The deal further noted that “the city and its officers maintain that they did not violate anyone’s civil rights nor act wrongfully or negligently during the incident.”

Before retiring, Mary Knowlton was the librarian at Parkview Elementary School in Rosemount from 1988 to 2004, then was a substitute librarian at other schools in the Rosemount-Apple Valley-Eagan district through 2013.

The Knowltons, who were married for 55 years, moved to Punta Gorda from Prior Lake, where they had lived since 1973. Knowlton originally was from Austin, Minn., where she went to high school. She then studied at St. Olaf College, the University of Minnesota and Minnesota State University, Mankato.