Marco Simoncelli: Steve Parrish on the accident
Immediately after I saw the crash involving Marco Simoncelli it was quite evident that it was very, very bad.
Motorcycle racing is very dangerous but nowadays we are not used to people dying because circuits are much safer and protective equipment is much better.
Sadly in this situation, instead of careering off into the big run-off areas and gravel traps, Simoncelli's bike veered back into the path of the following riders, American Colin Edwards and Italian Valentino Rossi.
Edwards' bike ran cleanly into Simoncelli's machine and Rossi just caught the edge of the accident.
I don't think any of the riders were sure of what was happening around them but one of those bikes unfortunately hit the back of Simoncelli's head, which took his helmet off.
That is very unusual, and it had to have been a huge impact for that to have happened.
At that point I think we all knew it was a serious accident. The helmet is the most important piece of any protective clothing - and if you lose that you're very vulnerable.
Marco was reported to be conscious in the medical centre in the early stages but, unfortunately, he succumbed to the injuries approximately 15 minutes afterwards. That was when we were informed that he had died.
There's nothing you can do about this kind of accident, when one bike crashes into another.
We sadly had the death last year at San Marino of Japanese rider Shoya Tomizawa in Moto2 but, unfortunately, it doesn't matter how safe you make the circuit. When you ride motorcycles at high speed, accidents can happen.
The riders don't ignore it but everyone knows it - and that's why they race. They know it's a very dangerous sport but they receive huge amounts of fun, excitement and adrenaline from doing it. That's what starts people riding motorcycles in the first place, they get a huge thrill from it.
But it doesn't take away from the fact that it is a tragic loss to the sport because Marco Simoncelli, in my opinion, was going to be one of the greats in the future.
He had huge amounts of talent having been 250cc world champion previously. He was at his prime and had just signed a contract to ride a factory Honda again next year.
I know he was ecstatic about the fact he would continue his relationship with Honda - and I definitely believe he would have been a threat to the World Championship next year.
However, I do think they will ride in Valencia for the final race in two weeks' time because it will be a big tribute to Simoncelli if they do.
My first thoughts - and this is absolutely my own gut feeling - are that Rossi could now retire. I know he will be mortified by Marco's death. They were close friends and had been for a long, long time.
He was involved in the accident and it will be very hard for him to cope with it.
Most importantly, my deepest sympathy goes out to all his family and friends after what was an extremely tragic accident that took the life of a very talented young rider.