Ronnie Ortiz-Magro, star of MTV's Jersey Shore, was arrested early Friday morning after allegedly striking his girlfriend and chasing after her with a knife, according to TMZ. The incident is reported to have happened around 2.30am Friday at a house in Los Angeles. Police reportedly received several 911 calls saying girlfriend Jen Harley was in distress. When the cops arrived, Ortiz-Magro had reportedly locked himself and his and Harley's infant daughter inside the house. Fearing for the child's safety, police reportedly broke down the door and tased Ortiz-Magro when he refused to cooperate. Cops took Ortiz-Magro to a hospital to get checked out and he's expected to be booked once doctors give him the all-clear.