According to the autopsy report, which was completed on Tuesday, Walker was a passenger in the Porsche Carrera GT and died from "effects of traumatic and thermal injuries."
The driver, 38-year-old Roger Rodas, succumbed to "multiple traumatic injuries," the report concluded.
The coroner's office told ABC News that two different doctors performed the autopsies. They found that Rodas died on impact, with Walker dying "maybe" a few seconds after from the combined effects of the impact and the fire.
Toxicology results on both men are expected in six to eight weeks. The deaths were ruled an accident by the coroner.
Walker, 40, and Rodas, were killed on Saturday in the crash near Rye Canyon Loop and Kelly Johnson Parkway.
The cause of the crash remains under investigation, but officials said the vehicle was likely speeding.
On Tuesday, new video of the crash surfaced. The surveillance footage apparently taken from a building rooftop showed a tree and light pole collapsing during impact.
Meanwhile, a makeshift memorial at the crash site continues to grow as friends and fans visit to pay their respects. Walker's recurring role in the "Fast and Furious" movie franchise helped catapult him to stardom.
Walker is survived by his 15-year-old daughter, Meadow.