LA MESA, Calif. -- A bullet grazed a 16-year-old skateboarder in the head during a robbery in La Mesa early Monday, police said.

The Arizona boy, who was visiting San Diego with his family, was wounded with a glancing shot to the head in the 7300 block of El Cajon Boulevard at about 1:50 a.m., according to La Mesa police.

The boy was riding his skateboard when the robbers stopped him, taking a personal item and a small about of cash, police said. It was not clear why one of the robbers shot at the teen.

The boy was taken to Sharp Hospital. His wound is not believed to be life-threatening.

Investigators were working with the San Diego Police Department to determine if the crime was related to a subsequent robbery spree in San Diego.

San Diego police said that between about 2 and 2:15 a.m., two gunman robbed at least three pedestrians in the Mid-City area. They were described as Hispanic males in their 20s with shaved heads, last seen driving a dark SUV with large chrome rims.