Our service actually had something like this happen several years ago. Our ambulance was parked outside the garage we usually park in at the ER because we didn't have a patient, we were just dropping off some paperwork. A mentally disturbed woman that was in the park across the street saw the EMT and paramedic go inside and got in and drove away. She drove it about 20 miles to a small town that she lived in. She told them that she followed all of the posted speed limits all the way to her house though .