A Mattapan man with a record for sexual offenses was arrested at Ashmont station this morning after a T inspector allegedly saw him following a female passenger while performing a lewd act.

According to a police report, Jerome Reed, 49, got off the Mattapan trolley in Ashmont around 9:30 a.m. on Saturday with his genitals exposed. The T inspector who observed this was "absolutely disgusted" by the "shocking and alarming" behavior, police say.

Reed is listed as "Level 3" sex offender, which means they have been convicted of sex crimes in the past and are prone to committing more.