Absolutely shocking. I can't believe Ward ran out on the track - probably out of fury, he wasn't thinking straight and ultimately got him killed.
About Stewart - I don't follow any of the American sports and have no history on him or what kind of a person he is, but being suddenly confronted with any driver out on the track running towards you... I can't possibly imagine anything other than pure instinct taking control and an attempt at some form of evasive action?
I wouldn't be surprised if perhaps earlier incidents led to this horrific accident... What looked a bit like an unfortunate incident (Stewart drifts into Ward who then touches the side and turns and damages his car) and then see him full of rage getting out of the car and onto the track....