The attempted hold-up occurred about 11:15 a.m. at Monaco Jewelers, 33955 Doheny Park Road, according to Orange County sheriff's Lt. Steve Doan.
"At some point in the robbery inside the store, one of the employees opened fire with a handgun, striking two of the three suspects," Doan said, noting that all of the bandits were wearing masks and gloves.
The third suspect escaped. As of 3 p.m., a SWAT team was searching a Costco store, the last business to be cleared in the area, Doan said.
"If we don't find him in the Costco, we're going to have to assume he fled the area in a vehicle,'' Doan said.
The suspect was described as a black man about 6 feet tall, wearing a white shirt and dark pants, Doan said.
Investigators were still trying to determine if the suspects also fired guns at store employees, Doan said.
It wasn't immediately clear if the hold-up was connected to two other jewelry store heists in the past several months in south Orange County, Doan said.
Doheny Park Road was closed between Del Obispo and Pacific Coast Highway during the search for the third suspect, Doan said.