A frantic 911 call from the man who fatally shot a 16-year-old shooter who killed a teacher and three students at an Oregon elementary school last month was released Tuesday.

In a tense call lasting a little more than a minute, Kaylub Giamanco told the 911 operator there’s “someone with a gun” at the school his daughter attends. “I have a gun and I swill shoot them right now,” said Giamanco, who was driving home for lunch and saw the shooter at Silver Rail Elementary School.

The operator implores him “don’t do anything, let me get an officer there.” They talk over each other and Giamanco sounds increasingly frustrated by the exchange. “I’m about to go kill this kid,” he said.

A few seconds later he says the shooter is entering the building. The operator asks if the shooter is firing and Giamanco says yes. The operator tries to get more information but the call ends.

A 16-year-old shot his way through locked doors to get into the elementary school in Bend, Oregon, on Oct. 15, killing three children and a teacher in a special needs classroom. Another student was critically injured and a teacher was injured and hospitalized.

A teacher tried to stop the shooter, Griffin J. John II, before Giamanco entered the school through an open window, opened the door of the classroom and fired his gun, dropping the shooter to the floor.