Investigators said Jasai Guy, 14, was shot in the chest around on Sunday morning at the Howard Houses on Osborn Street in Brownsville.
Police say Guy's younger cousin was visiting him at his home, and the shotgun went off in his living room.
First responders rushed Guy to Brookdale Hospital where he died.
Police are looking into the ownership of the weapon.
The 12-year-old boy is also facing charges of criminally negligent homicide and criminal possession of a weapon in the fourth degree.
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