By DAILY MAIL REPORTER
Heartbroken: Bam Margera returns to the spot where his best friend and Jackass co-star lost his life in a horrific car smash in the early hours of Monday morning in Philadelphia
Autopsy results reveal the crash was so violent it's impossible to determine if Dunn and passenger died from impact or from the fire that resulted
Photo emerges showing stuntman in high spirits whilst he partied at a bar shortly before crash
Co-star and best friend Bam Margera overcome with emotion as he visits crash scene
Ryan Dunn's Jackass co-star Bam Margera broke down into floods of tears as he visited the spot where his best friend lost his life in a horror 130mph car smash.
An inconsolable Bam spoke to a local news station and was so distraught he could barely put his loss into words.
'It was the worst phone call I ever got in my life waking up to that,' the 31-year-old wept.
Raw grief: Bam could barely hold it together as he gave an interview to a local news station
Margera, who was in Arizona at the time of the crash, visited the crash scene in Philadelphia on Tuesday evening.
He was visibly overcome with emotion, rocking back and forth in agony at the guardrail that the car crashed through.
'I've never lost anybody that I cared about. It's my best friend,' he told local TV station WPXI, weeping.
'Worst phone call of my life': He paid tribute to his childhood friend and asked how he would cope with the loss he wept: 'I can't, I can't'
'He was the happiest person ever, the smartest guy. He had so much talent, and he had so many things going for him. This is not right, not right.'
Margera stood at the guardrail that Dunn pierced with his Porsche Monday morning with such force that the car slammed through about 40 feet of trees before exploding into flames.
When asked how he'd get through this ordeal, Bam replied: 'I can't. I can't.'
Dunn's brother, Eric Dunn, said in an emailed statement to the AP that his family was 'devastated'.
Memories: The cast of Bam's show Viva La Bam, a spin-off from Jackass, featuring Bam, front centre, his father Phil, far left, mother April and Dunn, back centre which ran for five seasons between 2003 and 2005
Emotional: Close friends of Dunn visited the spot where his car smashed into a guardrail before careering off the road and into woodland and exploding into flames
In good spirits: A new picture shows Jackass star Ryan Dunn in high spirits as he parties at a bar with friends and fans shortly before he crashed his Porsche yesterday morning, killing himself and another passenger
Childhood friends: Ryan and Bam, pictured back in November 2003
Wreckage: The charred remains of the Porsche 911 GT3 is towed away as police survey the scene
Investigation: Dunn's Porsche was found engulfed in flames in woods beside the road
Margera, who appeared in her son's MTV show 'Viva La Bam' with Dunn, says he was not the type of person to get behind the wheel while drunk.
'He is going to be missed by everyone,' April tearfully told the NBC Today Show.
'I have yelled at him for lots of things but he was not a big drinker and he was always responsible as far as I know, so I cannot believe he would do that.
'I am sick because it is a waste, sick because I loved him, sick because he was talented and sick because he is gone.'
Meanwhile the passenger killed in Dunn's fatal car crash has been identified.
Police have confirmed Zachary Hartwell, 30, perished in a fireball car crash in the early hours of yesterday morning.
Hartwell, from West Chester, Philadelphia, had been with Dunn at Barnaby's and appeared in one of the last photographs to be taken of the daredevil before the accident.
The two were drinking with a third unidentified male in a Twitter picture, which was posted hours before the accident.
Speaking out: Bam Margera's mother April says she does not believe Dunn was driving drunk at the time of his death
While Hartwell was not a member of the Jackass crew, he is listed as a production assistant on the second Jackass movie.
He is also credited on IMDb as a 'car stunt driver' in Bam Margera's film Minghags.
He was reportedly a recently married Iraq war veteran
Dunn who was famous for his vulgar stunts in the multimillion-dollar TV and movie franchise Jackass, was driving his 2007 Porsche on a highway when it left the road, flipped over a guardrail and crashed into woods before bursting into flames.
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 unrecognisable except for a door that was thrown from the crash and not incinerated. A 100-foot-long tyre skid marked where the car left the road.
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 hosted Proving Ground on the G4 cable network.
G4 spokesman Dave Welch said Proving Ground, which premiered on June 11 with the second episode due to air today, was being shelved until the network could discuss its future.
Dunn's long-time friend and fellow Jackass daredevil Johnny Knoxville tweeted last night: 'Today I lost my brother Ryan Dunn. My heart goes out to his family and his beloved Angie. RIP Ryan, I love you buddy.'
Passenger: Zachery Hartwell (right) was killed in Dunn's fatal car crash yesterday. The pair were at a bar with an unidentified friend in Philadelphia before the accident
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'.
MTV praised Dunn's tireless humour 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 15 to Pennsylvania, where he met Bam Margera on his first day of high school, according to a biography 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.
Where the night started: Dunn and Hartwell were both at Barnaby's in West Chester hours before the accident
Dunn was working as a welder and petrol station worker when 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 bottom and going to a hospital casualty unit, 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.
In a 2000 stunt, he dived into a tank at a raw sewage plant wearing flippers, a mask and a snorkel.
Crash scene: Black marks on the road show where Dunn's car skidded out of control
Devastation: Dunn's car span off the road, through a guardrail and into the woods
Bam Margera Breaks Down After Hearing About Ryan Dunns Death