NEW FAIRFIELD, Conn. — During what appeared to be an attempted late-night burglary, a man fatally shot a masked teenager in self-defense outside his neighbor's house and then discovered it was his son, state police said.

Spokesman Lt. J. Paul Vance said Friday that police are trying to determine if the gun used by Jeffrey Giuliano, the father, was registered. It will be at least a week before the probe is done, he said.

Police said 15-year-old Tyler Giuliano was shot at about 1 a.m. Thursday in New Fairfield, a town along the New York line just north of Danbury.