How four people were killed in Kent State University Ohio?

There had been many people and students protesting the war all that week, they went so far as to burn the soldier education building on campus. Since the protest had gotten so out of hand, the national guard was called. Then on May 4th, by the Kent State victory bell, the protest went on, the national guard had surrounded the protest and were throwing tear gas into the crowd. The crowd soon was filling the tear gas cans with cement and throwing them back at the guard, the guard somehow had a miscommunication (as they put it) and fired. The shots hit 13 students, wounding 9, and killing 4.