The crime occurred around 2:10 a.m. in the 1400 block of Blue Jay Way, according to Los Angeles police.
Investigators say three suspects were in a car, and two of the men -- who were armed and wearing ski masks -- got out, forced two victims onto the ground and took watches and jewelry from them.
During the robbery, an armed security guard exchanged gunfire with the suspects and was shot in the stomach, police said. He was taken to a hospital in critical condition, police said.
The security guard is a retired law enforcement officer, officials said.
The crime victims also were shot, and were taken to a hospital in stable condition, police said. The victims were identified as men in their 40s, 50s and 60s.
The two wounded suspects got into their car and fled the area with the third suspect, police said. A description of the gray Audi was broadcast, and officers stopped it at Doheny Drive and Santa Monica Boulevard in West Hollywood.
One of the suspects was pronounced dead at that location, another was taken to an area hospital for treatment for a leg wound and the third was taken into custody.
Their names were not immediately released.
City News Service contributed to this report.