None of the store vendors contacted Tuesday would comment, and several people at the scene Monday declined to give their names because they said they feared retribution.
"It's just pure intimidation," Sgt. Tom Lorenz said of the group's robbery tactics. "I don't think anybody is going to get in their way."
Given the daytime hour and downtown location of the robbery, police are seeking more witnesses.
Police declined to confirm names listed on a booking report stemming from the robbery.
No weapon was reported, Lorenz said, but several witnesses exiting the store after the robbery were visibly shaken.
So far, none of the stolen jewelry has been recovered, the total of which hasn't been determined as detectives await inventory lists from the store, Lorenz said.
The shattered display cases were taped off in black plastic Tuesday. The store houses a variety of vendors who sell diamonds, watches and platinum jewelry pieces.
The jewelry store is no stranger to robberies.
In 2007, two men smashed the front-side windows of a jeweler's Toyota Camry after he left the store with a bag containing more than $300,000 in diamonds.
Witnesses reported seeing the suspects in Monday's robbery entering at least two cars, including a burgundy Buick, Lorenz said. They provided police with descriptions of the vehicles and suspects.
Police are lookng for multiple suspects, described as black, between 18 and 25 and driving a dark later-model Dodge Charger.
Anyone with details about the robbery is urged to call Glendale police at (818) 548-3987, or Glendale Crime Stoppers at (818) 507-7867. To remain anonymous, call the Los Angeles Regional Crime Stoppers' tip line at (800) 222-TIPS.