PHILADELPHIA >> "Jackass" star Ryan Dunn, who along with his cast mates made Americans cringe and snicker through vulgar stunts in their multimillion-dollar TV and movie franchise, was killed early Monday in a fiery car crash. He was 34.

Dunn, a daredevil who gained notoriety for diving into a sewage tank and performing other unsavory stunts, was driving his 2007 Porsche in suburban Philadelphia when it careened off the road, flipped over a guardrail and crashed into the woods before bursting into flames. A passenger, Zachary Hartwell, 30, of West Chester, Pa., was also killed, and speed may have been a factor in the crash, West Goshen Township police said.

The force of impact shattered the vehicle into several twisted and blackened pieces, leaving the Porsche 911 GT3 unrecognizable except for a door that was thrown from the crash and not incinerated. A 100-foot-long tire skid marked where the car left the roadway.

Both Dunn and Hartwell were severely burned. Police said they were able to identify Dunn through his tattoos and hair.

Dunn appeared on MTV shows "Jackass" and "Viva La Bam" and the three "Jackass" big-screen adaptations. He also was the star of his own MTV show, "Homewrecker," and just began hosting the show "Proving Ground" on the G4 cable network.

G4 spokesman Dave Welch said "Proving Ground," which premiered June 11 with the second episode slated to air Tuesday, was being pulled for now until the network can discuss the show’s future.

Dunn also starred in the yet-to-be-released film "Living Will." The film’s website describes Dunn’s character as a "party bum slacker (who) returns from the dead as a mischievous and perverted ghost."

Movie critic Roger Ebert tweeted about Dunn’s death Monday and was criticized by Dunn’s "Jackass" co-star Bam Margera and blogger Perez Hilton.

Ebert wrote: "’Jackass’" star Ryan Dunn, RIP. His Porsche flew through 40 yards of trees." He later tweeted, "Friends don’t let jackasses drink and drive," referring to a photograph Dunn posted on Twitter early Monday showing himself drinking with friends just hours before the 3 a.m. crash. The photo has since been removed.

"We understand what he’s trying to say," Hilton wrote, "but still — this is extremely insensitive!"

Margera erupted in expletives when he tweeted Monday night saying, "I just lost my best friend. I have been crying hysterical for a full day and…Roger Ebert has the gall to put in his 2 cents."

In a statement, MTV praised Dunn’s humor and enthusiasm and said he would be missed.

"We are devastated by the tragic loss of Ryan Dunn — a beloved member of the MTV family for more than a decade," said Van Toffler, president of MTV Networks Music/Films Group. "The Jackass brotherhood will never be the same."

Dunn was born in Ohio and moved at age 15 to Pennsylvania, where he met Margera on his first day of high school, according to a biography posted on his website.

Dunn, Margera, Christopher Raab (known as Raab Himself) and Brandon DiCamillo, under the moniker CKY for "Camp Kill Yourself," started making videos that featured them skateboarding and performing stunts.

Dunn was working as a welder and at a gas station when Johnny Knoxville, a friend of Margera’s through the skateboarding circuit, asked the crew to allow their videos to be part of the series "Jackass," which became a hit on MTV and ran from 2000 to 2002.

Perhaps his most famous stunt, in 2002’s "Jackass: The Movie," involved inserting a toy car into his rectum and going to an emergency room, where he made up a story that he was in mysterious pain after passing out at a fraternity party. Dunn’s X-ray from the hospital became a popular T-shirt for "Jackass" fans.

That first movie, filmed on a budget of just $5 million, went on to make more than $60 million in the United States alone. The most recent installment, released in 3-D in 2010, brought in $50 million on its opening weekend alone.

In a 2000 stunt, he dived into a tank at a raw sewage plant wearing flippers, a mask and a snorkel.

Autopsies were to be conducted Monday, though it was unclear when the results would be released.

According to court documents, Dunn was charged in April 2005 with driving under the influence after crashing his car in West Whiteland Township, about 2 miles north of Monday’s crash site. The documents show he successfully completed a program designed for first-time, nonviolent offenders that allows charges to be dismissed after defendants finish the program.