He says he was trying to defend himself and his sawed-off shotgun went off accidentally
Boston Police report arresting an alleged shotgun-toting 18-year-old in his 64 Mapleton St. apartment early Saturday morning:
Upon entering the location, officers learned that the shot fired emanated from the 3rd floor. Upon reaching the 3rd floor, officers made their way to a locked bedroom door. Officers proceeded to knock on the door until it was answered. When it was answered, the suspect told officers, “They were trying to kill me.” According to the suspect, he was attending a party on the 1st floor of the location when he bumped into an individual with whom he had had a prior altercation. In short time, the suspect says that he and the individual began arguing again. The suspect then stated that the individual and two of his friends chased him upstairs to his apartment. Once inside his apartment, the suspect says he ran into his bedroom, locked the door and grabbed the shotgun to defend himself. As he was grabbing the shotgun, the suspect says the gun discharged accidentally.
Anthony Inzoda, 18, of Brighton, was charged with the unlawful possession of a sawed off shotgun, unlawful possession of ammunition, discharging a firearm within 500 feet of a dwelling and unlawfully carrying a loaded firearm.
Innocent, etc.

Comments
Where are the feds?
Unlawful possession of a short-barreled shotgun is a federal offense (National Firearms Act). Something tells me he didn't purchase this through Class III Federal Firearms Licensed (FFL) dealer, paying his federal transfer tax on it.
So, hopefully the Feds can tack a few years onto the 60 days he'll do in Massachusetts.