It's said the cars were going 216 MPH when the accident happened.
Scheckter rocketed up behind Brack on the backstretch and tried to pass on the outside. Turn 3 was coming up way too fast for him to get around Brack, so he slowed a little and tried to pull into traffic. His left front tire made contact with Brack's right rear, sending his car sliding sideways. Scheckter's car acted as a lever and Brack's car rocketed off the track and hit the fence going 200+ MPH.
Luckily, the car did what it was designed to do and disentigrated. The motor can be seen tumbling down the track afterwards, ending up on fire near the infield grass. The tub that houses the cockpit was the only thing left resembling a racecar within 2 seconds of impact. It ended up on it's side near the middle of the track. I watched this live and it was a scary sight.
I'm happy he's still alive. I thought it was going to be a fatal accident, the way the car exploded like it did. Had it been one of the old Grand Prix racers, he would have been surely dead.
Let's hope he recovers.