HONOLULU -- Officers recovered a sub machine gun that police said was taken to Waipahu High School.

Investigators said that a student brought a gun to school to protect his girlfriend. The 14-year-old took a Mac-11 gun to school on Tuesday. It wasn't loaded, but the boy had the ammunition with him and knew how to operate the gun, police said.

The boy said two other Waipahu High School students were harassing his girlfriend and he planned to retaliate, according to police.

After school, another boy stole the gun from him, police said. The boy told police that he sold the gun for $60. Officers recovered the gun on Wednesday night.