Holy brains splashing. That was gruesome. Very vivid description. I would not be able to see all those details. I have noticed that in the few instances when I have witnessed accidents, my body/brain automatically shuts down and shuns away from the actual thing. I either close my eyes or turn around.
In one ocassion I was riding a bus and the bus hit someone and that someone was lying on the pavement. Most of the passengers either got off to see or stuck their heads out of the windown that gave them a good view. I got off and left. I was not paramedic, someone else had already called them. I had no business contributing to the chaotic crowd.
Your story made me evoke those instances. I don't have the stomach for that. i feel for those involved and it is certainly horrific not to be able to do more for them.