William Brennan, known as Billy, was 39 when he disappeared from the Glenwood Springs, Colorado, area in the spring of 1990. He was last seen on May 15 near Canyon Creek carrying a small duffel bag and wearing a raincoat. Reports at the time said he may have been in a suicidal state and that he might have had a handgun with him.

Brennan was a Vietnam War veteran, described as a Caucasian male with brown hair, blue eyes, a mustache and a purple scar near his left eyebrow. He stood 5 feet 11 inches and weighed about 220 pounds. A possible sighting in July 1990 reported him hitchhiking toward Las Vegas, Nevada, but that lead did not produce confirmation and he has not been located.

Anyone who saw William Brennan in May or July 1990, or who has information about his movements around Glenwood Springs or any travel toward Nevada, is asked to come forward.