Man defends home against twenty five gang members, but the story seems to be about the gun that he used

The man used an AK-47 to defend his home. I assume that it was a civilian version of the gun (i.e., a semi-automatic), and he was legally allowed to own it. The news article doesn't mention that this was a legal gun until the very end of the piece.

UNIONDALE, N.Y. (CBS 2) — He was arrested for protecting his property and family.
But it’s how the Long Island man did it that police say crossed the line.
He got an AK-47 assault rifle, pulled the trigger and he ended up in jail, reports CBS 2’s Pablo Guzman.
George Grier said he had to use his rifle on Sunday night to stop what he thought was going to be an invasion of his Uniondale home by a gang he thought might have been the vicious “MS-13.” He said the whole deal happened as he was about to drive his cousin home.
“I went around and went into the house, ran upstairs and told my wife to call the police. I get the gun and I go outside and I come into the doorway and now, by this time, they are in the driveway, back here near the house. I tell them, you know, ‘Can you please leave?’ Grier said.
Grier said the five men dared him to use the gun; and that their shouts brought another larger group of gang members in front of his house.
“He starts threatening my family, my life. ‘Oh you’re dead. I’m gonna kill your family and your babies. You’re dead.’ So when he says that, 20 others guys come rushing around the corner. And so I fired four warning shots into the grass,” Grier said.
Grier was later arrested. John Lewis is Grier’s attorney.
“What he’s initially charged with – A D felony reckless endangerment — requires a depraved indifference to human life, creating a risk that someone’s going to die. Shooting into a lawn doesn’t create a risk of anybody dying,” Lewis said.
Grier said he knew Nassau County Police employ the hi-tech “ShotSpotter” technology in his area and that the shooting would bring police in minutes. Cops told Guzman he was very cooperative. . . .
You may think a person has the right to defend their home. But the law says you can only use physical force to deter physical force. Grier said he never saw anyone pull out a gun, so a court would have to decide on firing the gun.
Police determined Grier had the gun legally. He has no criminal record. And so he was not charged for the weapon. . . .