Several videotapes have emerged in the area where
One video, obtained by CNN, does not show the car crash. But it shows what appears to be the car Walker was in hitting trees and knocking over a concrete light standard.
The security tape from a building across the street from the accident initially shows a small amount of smoke coming from the crash scene. Eventually, that gives way to full-blown fire.
In another video, the crash appears to occur behind some trees and cannot be clearly seen. That security tape -- obtained by TMZ -- shows smoke and eventually flames coming from the point of impact.
A third video, posted on YouTube, shows the immediate aftermath of the crash. The video shows the car fully engulfed in flames with debris on the roadway.
Authorities are continuing to investigate the cause of the Saturday crash in Santa Clarita but have said they believe speed was a factor.
Eyewitnesses have reported seeing only the red Porsche on the street when it hit a tree and a street lamp and burst into flames, according to the Los Angeles County Sheriff's Department.
"The only eyewitnesses to come forward saw a single speeding car," said Capt. Mike Parker.
Parker said the department had heard rumors about a street race in the area but had not been able to verify it.
Walker, 40, and his friend, whom witness Jim Torp identified as Roger Rodas, took a red Porsche out for a spin as a charity event held in support of Walker's organization Reach Out Worldwide was winding down.
Torp said he heard a loud boom and knew his friends had been in an accident. The smoke from the crash was visible from Always Evolving Performance Motors, which Rodas owned and where car enthusiasts and supporters were gathered -- some thinking it was just a fire on a nearby hill.
Jim Torp's son, Brandon, 28, grabbed a fire extinguisher and headed up the hill, followed by about 20 other workers, the elder Torp said.
"There was nothing they could do," he said.
The Los Angeles County Sheriff's Department on Sunday continued to investigate the single-car crash but did not reveal any details on a possible cause.