Updated

A 14-year-old boy admitted fatally shooting his father, a federal immigration agent, with his service weapon after arguing about school grades, a prosecutor told The Associated Press on Friday.

Prosecutors will seek to try the teen as an adult in the killing of Myron Chisem, 42, an Immigration and Customs Enforcement agent. The boy, whose name wasn't released because he's a minor, faces one count of murder with an allegation that he used a firearm to shoot his father.

The teen is expected to appear Monday in Juvenile Court. He remains in custody and it wasn't immediately known if he had retained an attorney.

Deputy District Attorney Todd Hicks said the teen admitted he shot his father after a lengthy interview with sheriff's investigators.

"Our working theory is apparently there was a dispute of some kind between father and son over grades," Hicks told the AP.

The teen used his father's weapon late Wednesday to fire a single round through a window from outside their house in Carson, near Los Angeles, authorities said. The bullet struck Chisem, a U.S. Navy veteran, in the back of his head.

Authorities said the boy then called 911, telling a dispatcher his father had been shot. The weapon was found in the front yard but it wasn't known how the teen might have gotten it.

It was Chisem's "practice to bring his weapon home and have it in the house," said Hicks, who declined to elaborate.

Chisem's friend, Shawn Butler, said the boy had moved into his father's house about six months ago.

Butler, who also has a teenage son, said Chisem never indicated there was any tension between him and his son.

Chisem was the second ICE agent killed in Southern California this year.

In February, agent Ezequiel Garcia was killed by a fellow agent after Garcia shot his supervisor at ICE offices in Long Beach. Garcia was being counseled on his job performance when the shooting occurred, authorities said.