If anyone was ultimately to blame, other than the Bill Ayers types who burned down the ROTC building, it was the Teamsters Union snipers who had been shooting at truckers in the Cleveland area during a wildcat strike in the days beforehand. The Guardsmen (mostly kids no older than the students at KSU) had been on duty there before being shifted to the campus.
Almost no sleep for 72 hours filled with legitimate fear of being shot, then having a rock throwing mob coming down a hill right at you, would lead lots of people to pull a trigger in that situation. I was a high school sophomore watching a baseball practice in the bright sunshine about ten miles from Kent when word came over the radio. One of those "never forget moments" like the Kennedy assassination.
Yeh, and after that, the Guard rarely gets live ammo.