Michael Frederick Griffin was born on September 11, 1961. At the time of the murder, he was 31 years old and described as a fundamentalist Christian and a loner with a bad temper. Griffin had become increasingly involved in anti-abortion activism and was influenced by John Burt, a former Ku Klux Klan member and the Northwest Florida regional director of the national anti-abortion group Rescue America. Burt was known for his extremist views and had been involved in the bombing of three abortion clinics in 1984. Griffin's association with Burt played a significant role in his radicalization.

On March 10, 1993, anti‑abortion activists were protesting outside Pensacola Women's Medical Services when Griffin, positioned near the clinic entrance, shot Dr. David Gunn three times in the back with a .38‑caliber pistol.

 Witnesses say he shouted, “Don’t kill any more babies” before firing.
Griffin was arrested immediately and charged with first-degree murder. During his trial, his defense attorney argued that Griffin had been brainwashed by John Burt, who had served as his "spiritual adviser." Despite this defense, Griffin was convicted of first-degree murder on March 4, 1994, after the jury deliberated for three hours. He was sentenced to life in prison without the possibility of parole for 25 years

In November 2017, the Florida Commission on Offender Review set Griffin's tentative release date for March 4, 2043. However, given the nature of his crime and lack of remorse, it is unlikely he will be granted parole.