The Confederation of Australian Motor Sport and the Western Australian Police will both investigate the tragic accident that claimed the life of Peter Brock.
Brock, and navigator Mick Hone, were competing in the Quit Targa West tarmac rally when the crash happened part-way through the second stage.
Reports indicate that Brock lost control of his Melbourne-built Daytona Coupe at a double-apex left-hander and made impact with a tree on the driver's side door at estimated 80 to 90km/h.
Spectator Les Andrews, who was first on the scene, told the Weekend Australian: "I took Peter's pulse from his left hand and I couldn't feel a pulse, and then I put Peter's hand in the navigator's."
"Eventually, after he kept on asking about Peter, I had to tell him his friend had passed away. I just stroked his shoulder and waited with him. Peter still had a tight grip on the steering wheel with his other hand, which I though was quite surreal...He looked very peaceful."
The accident happened about 40km east of Perth near the town of Gidegegannup.
According to fellow competitors the corner posed no drastic challenges and was not a high-speed test.
Speaking from hospital, the day after the event, Hone explained his version of the incident.
"We knew what was happening; we could see it coming," he said. "The car just got out of shape and he couldn't correct it in time..."
"Pete tried to correct it, but we just slid off the side of the road and basically collected the biggest gum tree there. It was one almighty bang as the middle of the car on Peter's side hit the tree."
The wrecked Daytona has been taken away by Police while they complete a forensic investigation into the accident, and the in-car footage and the car's MoTeC data recorder were being examined.
CAMS has also confirmed it will conduct its own enquiry.
"Obviously, we will work with the civil authorities to assist in their investigations," said CAMS President Colin Osborne.
Although Brock had only arrived at the event the night before, having flown in from the Goodwood Revival meeting in England, Police have ruled out fatigue as a factor. The Police are not expecting to finalise its report into the event for two weeks, while the CAMS investigation is set to run between six to 12 weeks.
Subaru, Mitsubishi and MINI withdrew from the event in the wake of the fatality.