Google 'Kent State'.
I have no reference, but IIRC I saw a poll taken among military personnel and the question of firing upon fellow citizens was "OK" by fourty five percent of those responding.
Don't bother. Kent State was Ohio National Guard sent in by the Ohio governor. I was a 19 year-old Marine when that happened and among active duty there was the general feeling that the guard was too ill-trained at that time to be doing riot control. Regular troops at that time would not have fired on that crowd under those conditions nor would their officers have given any orders to that effect. The guard of that day was far different from the force-integrated guard of today.
I was discharged fromn the Marines a month b4 Kent state.
The last days of my inlistment were spent on riot control,going thru tear gas once a week, and quick response deployments.
We were all Viet Nam vets and were trianing for the poor peoples march in Washington DC.
I’m glad we were never called because there would have been blood in the streets.
Kent state was terrible but would have been dwarfed by our actions. just sayin’.
Semper Fi