I love that you were able to apply your scout first aid training to help with that bleeding head in the boat crash. that's awesome.
Running away from or going toward an active shooter situation?(Or really, any dangerous situation in which others may be hurt) that's a toughie. My rule is save the family first, then help anyone else you can.
I took first aid years ago, but still have the basics. Breathing, bleeding, bones. Have been able to apply it on people a few times. Have used it many times on animals. Have used it tons of times on myself rather than submit to 8 hours of waiting in emerge when I know exactly what they will do and can perfectly do it myself.
J.L. Littlejohn is right. It really is heartbreaking when this is a subject that we can write about that is not fiction.