Officer Thierry was killed when he was assaulted by two inmates who were attempting to escape from the St. Louis County Jail. Officer Thierry was killed during a planned jail disturbance by inmates attempting to create a diversion to escape. Officer Thierry was found under a bunk with a sheet around his neck, his hands tied behind his back and a rag stuffed in his mouth. He was working overtime on his day off and was scheduled to retire in three days.

Officer Thierry was jumped when he entered a prisoner cell block to remove food trays. He was beaten with makeshift blackjacks fashioned by inmates from socks filled with bars of soap. Two inmates then pried a screen from a window of the outdated jail and attempted to escape with use of bed sheets tied together. The escape never succeeded as the first prisoner became stuck when his shoulders wedged in the narrow opening.

After a verdict of homicide by the St. Louis County Medical Examiner's Office, two inmates were subsequently charged by a St. Louis County Grand Jury with First Degree Murder and Escape Attempt. Both inmates were awaiting trial on robbery charges and had previous escapes from a state penitentiary. One inmate ultimately pleaded guilty to manslaughter and received a ten year sentence consecutive to life term for four counts of robbery.

Officer Thierry was survived by his wife. Interred: Gatewood Gardens Cemetery, St. Louis, MO.