Such ghastly scenes were uncommon, though IIRC one of the biggest mass killings in early 20th century US history was, in fact, at a school.
I would not say “nothing” was in the killer’s soul. The spiritual world, like nature, abhors vacuums. The devil was in that soul.
I think the Bath School mass murder is still the deadliest in U.S. history.
https://en.wikipedia.org/wiki/Bath_School_disaster