Jackass star Ryan Dunn's official cause of death was blunt and thermal trauma caused by the fiery car wreck that left him and a passenger dead, the Chester County Coroner's Office said Tuesday.

Toxicology tests - which could determine whether the 34-year-old West Chester native was drunk as his car veered off the Route 322 bypass in West Goshen Township - are not expected for four to six weeks.

Police released little new information Tuesday regarding Dunn's death or that of his passenger - 30-year-old Zachary Hartwell - as fans and friends continued to express their grief both publicly and in private.

Onlookers continued to flock to the site of the wreck - near the bypass' exit for Pottstown Pike - adding to flowers and cards already at the scene.

But the view was far different from the chaotic scene police found there Monday morning. Nearly 150 feet of curved skid marks suggest Dunn may have been trying to take the exit when his Porsche 911 GT3 careened off the road, through a guard rail and down a wooded embankment. The car flipped over, hit a tree and burst into flames.

The impact of that collision was so strong, police said, that it shattered his car into pieces. It was only recognizable, said West Goshen Township Police Chief Michael J. Caroll by a car door that had flown off of the chassis and managed to escape the flames.

Investigators believe Dunn may have been traveling at more than 100 miles per hour on the road which has a marked limit of 55. But have not said whether they suspect alcohol played a role in the wreck.

Hours before, he had posted a photo of himself and Hartwell drinking at a West Chester's Barnaby's of America bar. But bar manager Jim O'Brien said that the television star did not appear drunk.

Meanwhile Tuesday, Jackass star Brandon "Bam" Margera launched a Twitter tirade early against those using Dunn's death to make a statement against drunk driving before the facts come out.

His main target? Film critic Roger Ebert.

Within hours of Dunn's death, Ebert - a prolific Twitter user - posted his own judgments.

"Friends don't let jackasses drink and drive," he wrote.

Margera struck back with an expletive filled rant early Tuesday morning.

"I just lost my best friend," he wrote. "I have been crying hysterical for a full day and piece of s**t Roger Ebert has the gall to put in his 2 cents . . . Millions of people are crying right now, shut your fat f***ing mouth!"

Other members of the Twiteratti were quick to chime in, including bawdy celebrity blogger Perez Hilton, who called Ebert's comments in poor taste.

"We certainly agree that driving after drinking is wrong, we think there's no reason - especially RIGHT NOW - that anyone should be pointing fingers or poking fun at a truly tragic situation," Hilton wrote in a piece posted on his blog. "Everyone makes mistake, and this is somebody's son. Too soon, Roger."

By Tuesday morning, the backlash against Ebert had grown so heated that the social media site Facebook, temporarily removed Ebert's fan page in hopes of taming the vitriol. The page was reposted on the site just after noon.

In a post on his blog with the Chicago Sun-Times, Ebert stood by his comment but clarified it.

"I offer my sympathy to Ryan Dunn's family and friends, and to those of Zachary Hartwell, who also died in the crash. I mean that sincerely," he wrote. "I also regret that my tweet about the event was considered cruel. It was not intended as cruel. It was intended as true."

According to his official biography, Dunn, who moved to West Chester from Ohio at the age of 15, met Margera on his first day at West Chester East High School. The two quickly became fast friends, creating a group of stuntsters known as the CKY Crew - for "Camp Kill Yourself" - known for their cringe-inducing, gross out pranks.

Their antics along with boneheaded stunts devised by co-star Johnny Knoxville became inspiration for Jackass, which premiered on MTV in 2000 before going on to launch a franchise of three successful movies.

Dunn later went on to appear in such shows as Viva La Bam, Homewreckers, and the G4 cable network's Proving Ground, a show that premiered last week in which he tried to recreate famous stunts from video games and movies. The network pulled the new show from its schedule Monday in deference to Dunn's death.