"A briefcase containing a large dollar value of jewelry was stolen from him. And the suspects entered a vehicle and left the location," said Debra Herman, Los Angeles County Sheriff's Department.
The dealer's case was full of very expensive diamond engagement rings. During the fight for it, one assailant pulled a knife and stabbed the dealer in his left arm.
The wounded dealer was treated by paramedics at the scene and transported to San Gabriel Valley Medical Center. The wound was not life-threatening.
Police say the suspects all wore bandanas over their faces and dark hooded sweatshirts.
After stealing the briefcase full of rings, the suspects escaped in a brand-new red Toyota Camry.
Investigators have not given a dollar amount of the stolen rings, but they call it a significant loss.
Anyone with information is asked to call detectives at the Temple City Sheriff's Station. The telephone number is (626) 285-7171.