The robbery occurred just after 7:00 p.m. Friday night at Coast Food Market in the 1200 block of East Pacific Coast Highway.
Surveillance video shows the three robbers overwhelming the security guard with their weapons.
One of the suspects cocks his gun, then tosses a trash bag to the others, which they fill with cash before fleeing. The entire robbery takes 90 seconds.
Anyone with information on the crime or the suspects is asked to call the LAPD.