Instead of their friend, the home belonged to Lovell.

Lovell is a gun enthusiast whose Facebook page prominently features a picture of him aiming a gun, according to MassLive. Several posts reflected enthusiastic support for the Second Amendment, the website reported.

Lovell initially tried to communicate with the teenager knocking on his door, prosecutors said. But then he snapped.

"When a pane of glass broke, the suspect fired a single shot, striking the victim," according to the statement from the Hampden DA's office.

Richard Sawyer, a neighbour, said "a girl came running out screaming" after the gunshot.

"We have never had anything like this," Sawyer told MassLive. "We didn't know what it was."

Police said they were called to the house at 12:56 p.m. for a report of a breaking and entering, which suggests Lovell might have thought he was being robbed. It is unclear, however, if he was the person to call police.

"Upon arrival, our officers found a juvenile male, shot in the abdomen area," police said. "This victim was outside the residence. Our officers began emergency medical care, and he was immediately transported to Baystate Medical Center" but did not survive.

Authorities said they were waiting to contact the dead teenager's family before releasing his name.

Lovell's arrest stirred debate on social media about his decision to open fire.

Many pointed out that Massachusetts does not provide as wide protection for homeowners as other states. Massachusetts law states an occupant of a dwelling must act "in the reasonable belief that the person unlawfully in said dwelling was about to inflict great bodily injury or death upon said occupant or upon another person lawfully in said dwelling, and that said occupant used reasonable means to defend himself or such other person lawfully in said dwelling."

"Folks if you are gun permit holder, you better know the law!" Chicopee resident Brian J. Newton wrote on Facebook.

"People remember, you cannot use lethal force to defend yourself in less (sic) your life is in immediate danger, someone outside your home is not an immediate threat," added Christian James.

Mostly, however, locals rued how a series of small mistakes had upended two lives forever.

"This is a tragedy on all fronts," wrote Chicopee resident Cheryl Anziano. "There are so many things wrong here. A 15 year old drunk at 1:00 in the afternoon to start with (will the supplier of the liquor be charged?). Then there is the mistake of going to the wrong house by the boys. Perhaps the knocking got aggressive in order for the glass to shatter. Then you have a gun owner who doesn't know the rules of when you can and cannot shoot an intruder. The gun is discharged and with it two lives are ruined and the resulting ripples affect many others. I'm sure neither the child nor the adult woke up that morning with intended malice. I do wonder why the gun owner didn't just slam the door in the kid's face and call 911 while he was exiting the house by another exit."

"We knew something tragic happened but we did not know until later on that something so devastating happened," Betty Riel told local television station WWLP upon learning that the teen had died and Lovell had been arrested.

"I think it's very unfortunate at this time and tragic for both families to be going through this."

Washington Post