The medical personnel were helping an 83-year-old woman who had fallen about 3 a.m. when they heard beeping coming from the ambulance parked outside, indicating it was backing up, Longmont police spokesman Jeff Satur told The Denver Post.
"They ran out there and saw their ambulance driving off," he said.
Police were alerted and the emergency vehicle was spotted soon after. After a six-block chase, the unauthorized ambulance driver pulled over and was arrested, the Post said.
The suspect, Robert Elmar Taylor, 51, "was intoxicated and made some statement about being cold," Satur said.
Taylor faces charges of theft of the ambulance and driving under the influence of alcohol. There also was an outstanding warrant for his arrest for escape and he was listed as a missing person in Fort Collins, Satur said.