Malachi Heisler was protecting his mother against a masked intruder whom he shot dead, but the 18-year-old later realized the man was his estranged father.

The teen said he heard his mother calling out for help and he jumped out of bed and grabbed his rifle. Once he ran to his mother he saw a man in “SWAT attire” holding a gun to her head, and when the intruder pointed the gun at him, Malachi fatally shot the man in his head.

The Florida teen told WPTV, “I had about five to six seconds to make a decision,” adding, “By the time I did recognize him, the decision was made.”

Heisler’s mother had a restraining order on her estranged husband, John Heisler, after a previous armed break-in attempt, which was extended to May 2016. John Heisler’s gun were later revealed to be BB guns, but Malachi told WFLA that he was certain his father had broken in to kill him and his family.

“I had a feeling that something like this would happen but I didn’t know when. He wanted to scare us first, and then kill us while we were afraid.”