Detectives say it appears the man was already dead before the car was set on fire.
"Usually when we see cases of arson like this, the killers are trying to cover their tracks - burn the car, burn the body," said Lt. Paul Vernon with the Los Angeles Police Department.
Firefighters responded to a report of a possible dumpster fire shortly before 10:30 p.m. Monday along Garber Street near the 5 Freeway.
When they arrived on scene, they found a newer-model Audi A4 engulfed in flames. Firefighters put out the fire before flames spread to the trunk, where the man's body was discovered.
"When they opened the lid of the trunk, in there was probably a 5-foot-10, 6-foot-tall adult man," Vernon described. "Suspecting he's probably Hispanic and he was dead and probably had been dead for a few hours at least."
Detectives say the victim was between 25 and 35 years old. This identity was not immediately known.
Residents in the area are disturbed by the gruesome murder.
"I usually do my jog around here. All the time, I pass here. It seems safe. To find this out, it's something shocking," said Giovanny Mendez, an Arleta resident.
However, authorities say they don't believe the crime has ties to the neighborhood. It is not clear how the man died, but police say the murder is likely a result of drugs or gang violence.
If you have any information about this incident, you're urged to contact LAPD.