Klinger, All I can say is that thankfully, no-one was injured in this incident and I hope you never have to lay witness to such an event again.
I have never witnessed a fatal accident involving trains, but I have seen a b****y close one and some extremely stupid actions by people around the rail corridor while I have been out photographing trains around Moss Vale, NSW.
1: In 2008, I was at the crossing where a residential road crosses the single track secondary line from Moss Vale to Unanderra as a loaded export coal train hauled by a pair of 82 class diesels with between 40-50? loaded hoppers, each grossing 100 tons; and this girl only 16 or 17 years old on her learner's license drives out in front of the train (at this point only a few car lengths from her side of the crossing and running at maybe 20-30 km/h. The corner of the pilot misses the rear of the car by a very small margin and it's plain to see the driver of the 82 had all wits scared out of him.

What suprised me most is that the woman supervising the girl as per the provisions of a learner license (probably in her late 30s-early 40s) did not seem make any move to tell the girl to stop, nor did either pay any heed to the flashing lights and bells at the crossing, or the extremely obvious freight train that had right of way at the crossing.
For those not familiar with NSW driver's licensing, at 16 years old a person is able to obtain their learner's license which they have to log 120 hours of driving including at night with a fully licensed driver supervising them, and then have to spend 2 years on a provisional license and a further year on another, less restricted, provisional license before getting their full license.
2: On the 5/10/2008, I was photographing 3830, a 192 ton pacific type steam loco on a tour to Moss Vale. While 3830 and her crew were busying themselves with shunting and prepping the loco for the return, I noticed a man probably in his mid to late 40s jump off the platform, retrieve a bottle of lemonade and give it to a boy (who I presume is his son) after pulling himself back onto the platform, all this done without even looking to see if a train was coming
Having said this, I have seen some parents, grandparents, etc who were very aware of and acted very appropriately in ensuring the safety of their children. While the passengers from 3830's train were waiting on the opposite platform for 3830 to shunt the train for them to board, ARTC's Junee control centre decided to pass a southbound wheat train through the platform ahead of 3830. One pair of children were running about very close to the yellow line on the platform edge, not the appropriate action, on the kids part or their guardian's part for allowing them to play so close to the edge of the platform. In contrast, every other adult with a young child/children made a direct effort to ensure they behaved appropriately. When I heard the freight train approaching I went over to these two children and told them that there was a train coming and to get back from the edge and they ignored me; however their mother obviously heard me and took her kids back from the edge and held their hands. Every other parent/caretaker did a similar thing and all moved back a good 1 1/2 metres from the edge.
So as you can see, while there are far too many people who are stupid enough to not show care around the rail corridors, there are many who do take care.
My 2 cents.
Evan.