(Portland, OR) -- Portland police are looking for a sex offender who's described as having a history of violent behavior. Authorities say 56-year-old Dennis John Davis, who's wanted for a parole violation, removed his electronic monitoring device after he was released from prison Friday. Davis is described as white, five-feet-nine, 197 pounds, with gray hair and blue eyes, and police say he may have shaved his head. Anyone seeing Davis is asked to call 911.