The incident happened Tuesday on the 1500 block of Eagle-Butte Road. The victim is 39-year-old Christopher Demyen of Acton.
Authorities say it appears Demyen and the suspect got into an argument that escalated. Investigators say the 56-year-old suspect pulled out a gun and shot Demyen in the upper torso. Demyen was pronounced dead at the scene.
The suspect was arrested, but his identity was not released.
If you have any information about this incident, you're urged to contact the Los Angeles County Sheriff's Department's Homicide Bureau at (323) 890-5500.