On May 13, 1992, Sgt. Mahan became the first police officer in the city to be killed in the line of duty.
In the late evening hours on Tuesday, May 12, 1992, while responding to a disabled vehicle on U.S. Highway #1 in Port St. Lucie, Sgt. Mahan was struck by a passing motorist. Seriously injured at the scene, he was transported to the hospital where he succumbed to his injuries a few hours later on Wednesday, May 13, 1992. A seasoned law enforcement officer, Sgt. Mahan is survived by his wife Kelly, and children, Bradley, Courtney, parents Donald and Priscilla Mahan, and sister Laurie Haskins.
Born in Natrona Heights, Pennsylvania, Sgt. Mahan was a resident of Port St. Lucie since 1989, coming from Lake Park, Florida. He was a motorcycle officer with the traffic division of the Port St. Lucie Police Department and a member of the Police Benevolent Association in Port St. Lucie.
The Port St. Lucie Police Department was officially dedicated on June 29, 2001. The widow and the children of the Sgt. Donald R. Mahan laid flowers at the monument that was unveiled in front of police headquarters.