Salt Lake County Jail Sheriff's Office
Jon Kasai

SALT LAKE CITY — A man who police said assaulted his girlfriend's 14-year-old son after the boy refused to let him into the house has been charged.

Jon Kasai, 40, of Salt Lake City, was charged Thursday in 3rd District Court with child abuse inflicting serious physical injury, a third-degree felony, and child abuse involving physical injury, a class A misdemeanor, according to court documents.

On Nov. 15, Kasai went outside the home and the boy locked the door to keep him out "because he was drunk," charges state. The 14-year-old boy told police that his mother and Kasai have a history of domestic violence and that Kasai is a "violent drunk."

The boy was in the house at 90 E. 600 South with his younger sister. When the children's mother got home, she let her boyfriend into the house without knowing there had been a confrontation, according to police.

Charges state that after the boy locked Kasai out of the house, Kasai "pounded on the door" and shouted a threat, including an expletive, the boy told police.

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The teen had a knife in each hand when Kasai came into the house, according to the charges, and Kasai tackled him and punched him in the back.

During the fight, the boy sustained a cut to his neck and Kasai sustained cuts to his arms and back.

Kasai's attorney, Clayton Simms, told the Deseret News Friday that Kasai denies the allegations.

Kasai was disciplining the boy at the time of the incident, Simms said, when the boy pulled out a "12-inch butterfly knife" and Kasai tried to disarm him.