(Reuters) - A Connecticut man responding to his sister's call for help during an apparent burglary at her home next door, shot and killed a masked intruder who turned out to be his own teenage son, state police said on Friday.

Tyler Giuliano, 15, was wearing a ski mask and appeared to be armed when he was shot on Thursday by his father, who authorities declined to identify, said Lieutenant J. Paul Vance, a spokesman for the Connecticut State Police.

The father's sister, who lives next door, was home alone before 1 a.m. when she called him to report someone trying to break into her home. The father went over to investigate and was approached by a masked person dressed entirely in black and holding a shiny object, police said in a statement.

"Believing the suspect was armed with a weapon and about to attack him, the (father) discharged his personal handgun at the suspect," police said in the statement.

Giuliano was pronounced dead at the scene.

"(He) was lying on the ground in the driveway with obvious gunshot injuries, holding a weapon," the statement said.

Vance declined to further describe the weapon.

Authorities seized the father's gun, were investigating whether it is registered and will consult with the state's attorney to determine if any charges will be filed, Vance said.

Police also were investigating why the teen, who has no criminal history, was outside his aunt's home.

"We truly don't know. We'll look at the family dynamics, (his) school locker, cell phone, computer to figure out what's going on," Vance said.