*HUGS* What a terrible thing to come upon.

At least you stopped and it is great that the person responsible came back. I hope Missy will be okay.

To address your concern about no one else stopping, to be honest, if I saw a number of cars already on the scene, I'd likely keep going too. Too many cooks in the kitchen....

I've been yelled at by police or passerbys for offering to help when many cars/people are already on the scene. So if it looks like the situation is under control, I move on.

Now if someone was trying to flag down more help, then I'd stop and ask.