Video released by police show the two men chasing after a vendor, pushing him to the ground and punching and kicking him, then robbing him.
When bystanders try to help, one of the suspects waves a gun at them. Police say the suspect also used the gun to strike the vendor.
They got away with cash and a cellphone.
The two suspects fled the scene in a tan Mercedes-Benz coupe, shown in photos released by police.
The incident happened on Monday around 4:20 p.m. in the 1400 block of Locust Avenue.
The suspects were described as 20 to 25 years old and 5 feet 6 inches tall. One was dressed in a black hoodie and khaki pants, and the other was dressed in a gray sweater and light blue pants.
Anyone with information is asked to call LBPD Robbery Detective Eric Hubbard at (562) 570-7464. Anonymous tips may be submitted through "LA Crime Stoppers" by calling 800-222-TIPS (8477), downloading the "P3 Tips" app to your smartphone (available at the Apple app store or Google Play), or by visiting www.crimestoppers.org.