Dec. 2, 2013 -- Investigators are working to determine the cause of a fiery crash that killed "Fast & Furious" star Paul Walker and his driver-friend as fans gathered at the crash site to erect a makeshift memorial in honor of the actor.
Sheriff's deputy Peter Gomez said Sunday investigators hope to learn how fast the 2005 red Porsche Carrera GT was traveling and what caused it to go out of control, including whether the driver was distracted or something in the road prompted him to swerve.
The crash also killed Walker's friend, professional driver Roger Rodas, according to Walker's publicist, Ame Van Iden. She said Walker was a passenger in the car when they drove away from a fundraiser in the community of Valencia Saturday. The two bodies were so badly burned that officials said they would use dental records to make a postive identification.
Walker, 40, and Rodas, 38, had thrown a fundraiser benefiting victims of the recent typhoon in the Philippines. The event was held by Reach Out Worldwide, a charity Walker founded in 2010 to aid victims of natural disasters.
The crash happened in a business park just a few blocks away from the charity event. The Porsche smashed into a light pole and tree. Sheriff's deputies found the car engulfed in flames when they arrived. Witnesses tried to put the fire out, but both men were pronounced dead at the scene.
Jim Torp was at the charity event and spoke to both men just before they rode off.
"'Hey, I'll be right back in 5 minutes.' Those are the last words I heard," Torp told ABC News.
Police tell ABC News the impact of the crash was so great, a chunk of the car flew several feet into a nearby building, breaking a window.
Rodas and Walker co-owned an auto racing team. Rodas competed in 10 Pirelli World Challenge GTS races this year, the racing organization said in a statement.
Torp said Rodas was an accomplished pro racer who was accustomed to driving fast cars.
"…That's why I am shocked. He's driven cars that's faster than this..." Torp said.
Mourners visited the crash site Sunday and left flowers, candles, DVDs and other memorial from the "Fast & Furious" franchise that launched Walker to stardom.
"He was a very good actor and a very good person. I did meet him in Santa Barbara when I lived out there and he was so sweet and so kind and so down to earth," Nathalie Hoist told ABC News Radio.
PHOTOS: Paul Walker's Life and Career
Walker's "Fast & Furious" co-star Tyrese Gibson broke down when he visited the crash site.
Walker has been on break from filming "Fast & Furious 7," the latest installment in the "Fast & Furious" franchise which has been one of the most successful in recent memory. Universal Pictures has not said what it plans to do with "Fast & Furious 7," which was slated for release in July.
"The real question is how long they are going to take to figure out the direction of the film and to make everyone comfortable with coming back to work," Hollywood Reporter executive editor Matthew Belloni said.
Walker had recently finished work on "Brick Mansions," which was in post-production. Another film, "Hours," a drama about Hurricane Katrina and its aftermath, was due to be released Dec. 13.
Walker is survived by his 15-year-old daughter, Meadow. The actor was never married.
The Associated Press contributed to this report.