NEW FAIRFIELD, Conn. — A popular fifth-grade teacher fatally shot a masked teenager in self-defense outside his neighbor's house during what appeared to be an attempted late-night burglary, then discovered the teen 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.

Tyler Giuliano, described as an easygoing 15-year-old who enjoyed flying small planes, was shot at about 1 a.m. Thursday in New Fairfield, a lake community of about 14,000 along the New York line just north of Danbury.

"It's something out of a Hollywood script," said First Selectman John Hodge, who doesn't recall another killing in his eight years on the job. "You certainly don't expect it to happen in your own small hometown where there's very little crime."

Jeffrey Giuliano's sister, who was alone in the home, believed someone was breaking in and called Giuliano, who lives next door, state police said. Giuliano grabbed a gun and went outside to investigate, troopers said.

He confronted someone wearing a black ski mask and black clothing and then fired his gun when the person went at him with a shiny weapon in his hand, police said. They would not provide details about what kind of weapon it was.

When police officers arrived almost immediately after they were called, the teen was lying in the driveway of his aunt's home with gunshot wounds and the father was sitting on the grass. The teen was pronounced dead at the scene, police said.

A state trooper pulled back the ski mask to reveal that the victim was Tyler Giuliano, though it was unclear if Jeffrey Giuliano already knew that. It was also unclear if he was actually trying to burglarize the house or if it was some type of prank gone wrong.

"All in all it's a tragedy," Vance said.

Jeffrey Giuliano hasn't returned a message seeking comment on what happened. Alicia Roy, superintendent of schools in New Fairfield, said Giuliano is a native of the town who offers summer music and zoology camps for his students and plays in a band that raises a lot of money for charity.

"''He wanted to teach in the community (where) he grew up," she said. "He connects with the students. He's a caring person. Very interactive class."

Tyler Giuliano was a student at New Fairfield High School, a short walk from the neighborhood where he was killed. Roy said he was a member of the Civil Air Patrol and was described as an easy-going young man who enjoyed spending time with his family. During a storm last year, he volunteered at a shelter set up the local high school, helping to serve meals and set up cots.

Roy said Tyler especially enjoyed flying gliders and single-engine planes out of Danbury airport.

"He would fly as many hours as possible," she said.

No charges have been filed. An autopsy is planned.