The accident took place Saturday in Santa Clarita, California, reports tmz.com. Walker was said to be inside the Porsche GT when the driver somehow lost control.
He was in Santa Clarita for a car show to support the Philippines typhoon relief effort, and went for a ride with a friend in a new Porsche GT. The accident happened during that test spin.
"He was a passenger in a friend's car, in which both lost their lives," Walker's representative said in a statement.
The representative added that Paul was "attending a charity event for his organisation Reach Out Worldwide."