Originally Posted by CingularDuality

Holy crap, there's a guy on foot that gets blown out of his jumpsuit while trying to cross the track! That is some incredible footage. It's amazing what man will do for a thrill....

The incident you're referring to was during the Grand Prix at Kyalami, South Africa, 1977. What you're seeing actually is the marshal's body being torn apart. This is, without a doubt, the most gruesome crash footage I've ever seen. Also among the most tragic as the full extent was was so freakishly improbable, yet so easily avoidable.

Here's as good a summary as I've found anywhere (source, Tom Pryce - Wikipedia)...

At the end of lap 21 of the Grand Prix at Kyalami, South Africa, on March 5, 1977, Pryce's teammate, Renzo Zorzi, retired his Shadow with a split fuel pipe which had caused a small, but harmless, fire. Zorzi's car was parked in a blind brow but two teenaged marshals stationed on the opposite side of the track decided to cross to extinguish the fire. At that moment, Pryce and the March of Hans-Joachim Stuck suddenly appeared, nearly side-by-side. Stuck's car passed behind the first marshal and ahead of the second marshal, 19 year old Jansen Van Vuuren, who was sent by the head marshal to assist Zorzi in extinguishing the flames. Pryce however could not avoid Van Vuuren, hitting him at high speed and killing the marshal instantly. The impact seemed to have only minimal influence on Pryce's car, only slightly damaging its front wing. However, the fire extinguisher Van Vuuren was carrying struck Pryce on the head; the impact tore off Pryce's helmet and nearly decapitated him, killing him instantly. Pryce's car continued down the straight track, gradually slowing down and verging to the right. Jacques Laffite, who was unsure what was going on, moved alongside as the two cars approached Crowthorne, at that point Pryce's car skidded off the barriers, back on the track again, where it hit Laffite's Ligier, taking Laffite out of the race but not injuring him. As for Van Vuuren, the injuries to his body were extremely severe. It was identified only by exclusion, after the race director summoned all of the race marshalls and Van Vuuren could not be found.