Police say the three men burst into Rush-A-Fix Jewelry & Watch Repair before 2 p.m. and used pepper spray on a clerk and a customer, a woman in her 20s.
"They were coming out blinded, gagging, throwing up," said witness Edward Howton.
The suspects busted open display cases and were able to take off with an unknown amount of jewelry, according to Long Beach Police Sgt. Aaron Eaton.
"It was a very fast robbery, a way to get in and get out," he said.
The clerk and the customer are expected to be OK.
Police say the three suspects left the store in a light-colored SUV. Anyone with information is asked to call Long Beach police at (562) 570-7464.