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One teen was dead and another hospitalized after a group of three boys allegedly beat and tried to rob an off-duty U.S. Customs and Border Protection officer in Arcadia on Friday, officials said.

The three teens, between 14 and 15 years old, attacked the officer from behind as he was walking on the sidewalk along 1st Street, south of Colorado Boulevard, around 8:15 p.m., according to a statement from the Los Angeles Sheriff's Department, which is investigating the incident. Officials had originally reported the assailants were men.

One of the boys allegedly hit the officer's head several times while another pointed a handgun at him and demanded his property.

The officer believed the teens were going to rob and shoot him and pulled out his CBP-issued handgun.

He shot at the boys, striking a 15-year-old who was holding the handgun as well as a 14-year-old, sheriff's officials said.

Both suffered multiple gunshot wounds and were taken to a hospital, where the 15-year-old was pronounced dead at 5:34 a.m. Saturday, deputies said. The 14-year-old remained hospitalized Saturday with injuries that were not life-threatening.

The third boy, also 14, was not hit and able to flee. However, he was later located at a residence near the scene and arrested on suspicion of robbery.

The officer sustained some bruising to his face but did not require medical treatment.

The handgun used by the 15-year-old was recovered at the scene, authorities said.

Deputies did not release the officer's name or details about his position. The assailants' identities were concealed due to their age, but the mother of the teen who died said his name was Darius Smith.

Reshawna Myricks told KTLA her son wouldn’t have been involved in a robbery.

“I know my child, that’s not my child,” she said.

Correction: This story has been updated to clarify the officer's position.

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