A 21-year-old man was arrested Tuesday on suspicion of exposing himself at a middle school in Mountain View earlier this month and possessing child pornography. Police issued an arrest warrant for Christopher Galbreath on Tuesday after linking him to the Dec. 2 indecent exposure incident.A 13-year-old female student at Graham Middle School reported that Galbreath, a part time aide at the school, had exposed himself to her in an empty classroom, according to police. Officers were not able to locate him immediately. Galbreath has also been charged with possession of child pornography after detectives allegedly found such materials on his computer. He was booked into county jail and given an initial bail of $35,000.Police believe Galbreath may have exposed himself to other girls in the past and ask anyone with information about the case to call the Police Department at (650) 903-6395.