The LA coroner revealed results of an autopsy on the actor, who was killed in a car crash along with a friend.
The driver of the Porsche Carrera GT, Roger Rodas, died of multiple traumatic injuries, the coroner said.
The coroner ruled that both deaths were accidents and said that the injuries occurred when the car struck a fixed object.
It comes as video from a nearby building emerged showing smoke from the initial crash and then later a large fireball explosion that lights up the sky.
The LA coroner released the autopsy findings for Walker and Mr Rodas
As a result of 40-year-old Walker's death, Universal Pictures has announced it is putting filming of Fast & Furious 7 on hold indefinitely.
The studio said in a statement: "At this time we feel it is our responsibility to shut down production on Fast & Furious 7 for a period of time so we can assess all options available to move forward with the franchise."
More than half the movie has reportedly been made and it was slated for release on July 11, 2014.
Walker had been a passenger in the Porsche when it smashed into a lamp post and tree before bursting into flames, said Walker's publicist.
Tributes to Paul Walker at the scene of the crash
But their enquiries have been hindered by the crowds of fans that have continued to flock to the crash site.
Investigators do not believe Mr Rodas and Walker had been racing another car, but they were speeding on a street with a 45mph limit, said Los Angeles County Sheriff's department.
The mangled wreckage of the Porsche after the smash
While the neighbourhood where the tragedy happened is known to attract street racers, police said they had no indication of a second car being involved in the smash.
Before the crash, the pair had been at a charity fundraiser event at Mr Rodas' car shop and later left, saying they were going on a brief drive which turned out to be fatal.
