The incident happened in the last gasps of the race with Prost leading. However, Heidfeld was gaining and got a strong drive out of the previous corner. He lined up by Prost to attempt the pass, when Prost turned into Heidfeld's car. That move pitched Heidfeld's car sideways and turned the curb into a ramp to launch him into the wall in a very scary looking crash.
In the exterior shot in the video, you can clearly see that Prost checked his right mirror from the cockpit before turning, but evidently he didn't notice Heidfeld drawing alongside him on the other side. Thankfully, Heidfeld was not seriously injured, and Lucas Di Grassi was able to drive around the two stricken cars to take the victory.
While crashes like this in motorsports are never positive because they put drivers in serious danger, an incident like this with no major injuries could actually work to give Formula E some notoriety – particularly among those who don't follow racing religiously. If nothing else, the crash vividly illustrates that the series' drivers are willing to put it all on the line. Both men have weighed in on Twitter about what happened:
I feel very bad about the incident and after looking at the videos I understand that I am responsible. I just did not see him, feel very bad- Nico Prost (@nico_prost) September 13, 2014
The most important thing is that my friend @NickHeidfeld is ok, sorry again Nick, you know I would never do something like this...- Nico Prost (@nico_prost) September 13, 2014
Just to let everybody know: I am fine... physically... Could/would/should have won that. Now nothing... #racing- Nick Heidfeld (@NickHeidfeld) September 13, 2014