Police said the suspects walked into the Fullerton Jewelry Mart on South Harbor Boulevard in pairs at about 4:45 p.m., and then started smashing cases and grabbing jewelry.
The whole thing took less than a minute.
Some of the people inside tried to fight back. One man was seen on surveillance video throwing a chair at the suspects.
The only description of the suspects is that they were black men in their early 20s. Anyone with information is urged to call the Fullerton Police Department at (714) 738-6800.