ST. PETERSBURG, Fla. (KRON/AP) – Investigators say a teenage boy shot and killed a ski-mask-wearing home intruder who ended up being his own father.

The Pinellas County Sheriff’s Office said early Tuesday morning 46-year-old John Heisler broke into the St. Petersburg home where his former girlfriend lived, along with their teenage son and the teen’s younger sister.

Investigators say Heisler grabbed the woman, prompting her current boyfriend, who was in the home at the time to call out for help. That’s when the 18-year-old son emerged from his bedroom with a gun.

The teen told police Heisling pointed the gun at him and his mother and that’s when he opened fire.

He said he only had seconds to make a decision and initially didn’t know who the masked man was until after he fired the gun.

Heisler was pronounced dead at the scene. No charges have been filed.

Authorities say the boy’s mother had obtained a temporary restraining order against Heisler in April.