Plausibility

In response to the commenter on Facebook saying guns don't go off when dropped, I'm aware of an incident when that was definitely what happened. In a U. S. college classroom, as class was letting out; a young woman dropped her purse and the pistol inside discharged. The bullet went through the writing desk attached to the chair in front, and the sleeve of the student sitting there, and embedded itself in the ceiling tiles over the instructor's head. The gun was a "Saturday night special" and the safety was too stiff for the owner, so she kept it off. Faculty who taught the next period—after lunch—did an informal survey of their students and almost all were either carrying in the classroom (despite "no guns" signs posted in every classroom) or had long guns in their vehicles. The students pointed out that there had been an abduction from campus the previous week.

If a gun accidentally discharges, very low probability of 4 injured. Just curious as to the demographics of that school. Another White Supremacist?

I don't think we have anywhere near enough details of the situation to make a call of implausibility on the accidental discharge. The local police, who did have details, were inclined to accept it was accidental.

I'd be very doubtful that it was white supremacy-related.