Mary Knowlton was one of two volunteers randomly chosen to participate in a shoot-don’t shoot exercise, but was killed Tuesday night when a Punta Gorda, Fla., police officer shot her multiple times with live ammunition rather than blank rounds. Knowlton was playing the “bad guy” in a scenario that was intended to demonstrate the split-second decisions police have to make on the job. The exercise was part of the Citizens Academy event, an eight-session, interactive course for local residents that attempts to teach them about the roles of various city departments and services. About 35 people were taking part in the Tuesday event.

According to Punta Gorda police public information officer Lt. Katie Heck, the shoot-don’t shoot scenario has been part of the program for 2 years. “We have done them for the last two Leadership Charlotte police nights, Punta Gorda Citizen’s Academy, and then this was the first police night hosted by our Chamber of Commerce. In each session, four individuals went through the scenarios with no injuries or incident.”

Knowlton was rushed to a nearby Fort Myers hospital, where she was pronounced dead. The Florida Department of Law Enforcement is investigating the killing.

Mary Knowlton’s Facebook page said she lives in Punta Gorda but had been a librarian in Savage, Minn. A longtime friend said that Knowlton had a love of books and tried to instill that in children. “So much is on the Internet now,” said Carolyn Hartwigsen. “But, books are so important to have in children’s hands. That was important to her.”

Police Chief Tom Lewis said he was “devastated for everyone involved in this unimaginable event.” The police officer involved in the shooting has not been identified, and has been placed on administrative leave while an investigation takes place.