I remember this happening. I didn't start following F1 until the year after, but I remember this being shown on the news later that evening.
I was shocked at what I saw, I seem to remember footage of him lying on the track surrounded by medics, his helmet had been removed and his whole face and neck was deep purple. This was the first time I ever saw a dead person, I found it very disturbing. It's all the more sad when you think he was still angry with Didier Pironi from the previous race.
It would have been nice to see him racing alongside Ayrton Senna had he been around in 1984. Alas we will never know.
As it says on the track at Canada, 'Salut Gilles'