Lieutenant Gillis was shot and killed while off duty while attempting to disarm a drunk a and disorderly man while camping in the Laguna Mountain Recreation Area with his wife. The man had come into his campground after becoming separated from his hunting party. Lieutenant Gillis tried to help the man find his party but was unsuccessful. He then told the man to get into his car and sleep it off and that they would try to find the party again in the morning.
The suspect then grabbed a rifle and fired into the air twice. Lieutenant Gillis grabbed the rifle and headed towards his station wagon. When he turned around to the face the man again the suspect grabbed a second rifle and shot him in the chest. The man was apprehended and sentenced to life.
Lieutenant Gillis had been with the agency for 20 years and was assigned to the Firestone Substation.