PORTLAND, Ore. (AP) -- Portland police arrested a homeless man who spent the night sleeping in the back of a patrol car and then couldn't get out. Sgt. Pete Simpson said an officer was in the Southeast Precinct parking lot Tuesday morning when he heard someone yelling from an unattended police car. In the back seat was Ruben James Turner III, who told the officer he accidentally locked himself inside after deciding to sleep in the vehicle. Unlike a regular car, the back seat of a patrol vehicle is a secure custody area and has no handle to get out. "Once you shut that back door, you're essentially in a cage," Simpson said. The precinct is not staffed 24 hours, so Turner couldn't get rescued until morning. He tried, however, by writing "Help" with his finger in the window condensation. Simpson said the police car had been accidentally left unlocked, allowing access to the front seat, which has a lot of equipment. Turner rummaged through the glove box and unhooked the mobile data computer before heading to the roomier back seat. Nothing was stolen, but the officer discovered foam padding had been ripped from the headliner and around the plastic seats, said Simpson, who did not have a damage estimate. The 30-year-old was booked into the Multnomah County Jail on charges of criminal mischief, criminal trespass and unlawful entry into a motor vehicle. "It's safer than a lot of places and perhaps more comfortable than cold, wet pavement," Simpson said. "But it's definitely not a place most people would seek to sleep."