Police responded to the smash-and-grab at Prestige Jewelers on Saturday shortly after 12:30 p.m. No injuries were reported.
Investigators say the robbers used hammers to break display cases and steal jewelry.
The suspects took off in several cars waiting outside after the store's employee shot at them, police say.
A description of the suspects was not immediately available.
Anyone with information should contact Detective Hartnell at (310) 802-5127 or the Manhattan Beach Police Department Tip Line at (310) 802-5171. Those wishing to remain anonymous can contact Crime Stoppers at (800) 222-8477, or www.lacrimestoppers.org.