According to police reports Ryan died due to injuries sustained in the crash. His Porsche drove of the road and caught fire. Another, anonymous person was in the car with Ryan and died as well.
Flickr shows photos of the burnt out wreckage. Hours before, Ryan posted a photo of himself, drinking with friends.
Dunn featured in Jackass and in the three Jackass movies. He also had his own show Homewrecker and he often showed up in Bam Margera's spin off series Viva la Bam. Two of his most memorable Jackass stunts were diving into a local sewer and inserting a toy car up his *ss (wow, just wow....). RIP Ryan.