Armed Robbery ArrestDarion Carrington, 17, of Dorchester was arrested after he struck a victim in the head with a baseball bat and then robbed him. The incident occurred at 4:45pm yesterday at Walnut Avenue and King Boulevard in Roxbury. Officers located Carrington on Dale Street (Roxbury) after witnesses provided a description of the suspect. Carrington will be arraigned in Roxbury District Court on Monday and charged with Armed Robbery. Unregistered Sex Offender At 5:55pm yesterday, while conducting an investigation at Morton Street and Evans Street in Mattapan, officers arrested Roy Irby, 34, of Mattapan for failing to register as a sex offender. Irby will be arraigned in Dorchester District Court on Monday. Gun & Warrant Arrest 12:46am on Saturday, 4/29/06, officers pulled over a motor vehicle with inoperable brake lights on Franklin Hill Avenue at American Legion Highway, Dorchester. Officers discovered one passenger, James Prince, 24, of Brockton had a default warrant out of Brockton Court for Possession of Class B in a school zone. While placing Prince under arrest, officers observed a firearm under the drivers seat and recovered a loaded 45-caliber handgun. Stephen Gillis, 26, of Stoughton was placed under arrest for Unlawful Possession of a Firearm & Unlawful Possession of Ammunition. Both parties will be arraigned in West Roxbury District Court on Monday.