A 29-year-old Japanese visitor sustained serious injuries when he attempted to stop suspects who allegedly targeted his mother in a purse-snatching in Waikiki.

The robbery occurred near the Waikiki Sand Villa Hotel on Ala Wai Boulevard at about 10:30 p.m. Monday.

Police said two male suspects exited a vehicle and grabbed a bag from a 63-year-old woman.

Her son intervened. Police said the perpetrators assaulted him and fled in a vehicle occupied by two other male suspects.

A source said the victim was struck in the face with the butt of a pistol.

Police and Emergency Medical Services responded. Paramedics treated the victim for an eye injury and possible head injury. He was taken to a hospital in serious condition.

Descriptions of the suspects were not immediately available.

Honolulu police have launched a first-degree robbery investigation. There are no arrests at this time.