A convicted sex offender is back behind bars after authorities say he plastered pornographic pictures on cars parked at Burien City Hall in August and September.

Noah Nelson, 31, was charged Monday with possessing depictions of minors engaged in sexually explicit conduct and cyberstalking.

Last month, Nelson was caught on a security camera driving up to cars on his scooter and leaving porn on the cars of strangers, according to court charging paperwork. Burien police installed the hidden camera in the city parking garage after the pictures were left on the car of Finance Director Gary Coleman and other city employees.

Images of the suspect were circulated to local police agencies, and an officer with the state Department of Corrections recognized the man as being on probation, charging papers said. When police searched Nelson's home on Oct. 7 they found pornographic DVDs and printouts that were similar to the pictures left in the parking garage, court paperwork said.

Nelson told police that "he has been addicted to porn since he was 14-years-old and has recently transitioned to child pornography," charging papers said.

Nelson was charged with cyberstalking after authorities say he sent a pornographic image to an acquaintance over Facebook.

Nelson was convicted in 2007 of first-degree child molestation and attempted child molestation, said King County Senior Deputy Prosecutor Charles Sergis in charging paperwork. He is being held at the King County Jail on $100,000 bail.