My thoughts go out to everyone involved in this, the innocents especially, the children, the husband, the engineers, the emergency responders who had to clean up this mess. To all of them go my deepest condolences. However like many responders here I feel little or no pity towards the woman who negligent actions brought the pain and suffering on those still living. I hope the children pull through, the husband comes to terms with his wife's actions; what a mixed bag of emotions he must be going through, anger for her stupidity, pain for the loss of the woman he loves, confusion as to why she ran the crossing. The engineers, for as EasyE said it would have all been in slow mo' for them.
Back in the UK I had a friend whose father was a tube driver (subway). He had a jumper in front of one of his services, he couldn't even talk about it to his family, I can only imagine what the combination of 10's of thousands of volts from the third rail and the kinetic impact of the train would do to a human. He never went back to work because of it, he found another job within London Transport.
Sadly this happens often enough to almost warrant 'commonplace' it probably won't make it into the Darwin Awards. But unfortunately it's right up there with some of the saddest.