The man was found mortally wounded Wednesday afternoon near a home at 15808 Roxford St., the Los Angeles Police Department said. The victim was pronounced dead at a nearby hospital.
The property included several horse stables, where officers found "two bricks of cocaine," Lt. Paul Vernon said.
"It appears this was either a drug deal gone bad or a drug rip-off," said Vernon, commander of the Mission Division detective unit.
Witnesses reported seeing a silver Mercedes Benz at the home and hearing gunshots. The victim staggered outside and collapsed nearby as the vehicle sped away, police said.
At least 22 homicides have been reported in Sylmar since 2007, according to a Times Homicide Report database.
Anyone with information is asked to call the LAPD at (213) 838-9976. Anonymous tipsters can call (888) 222-8477.