Criminal law makes a distinction between gross negligence (locking the doors to a busy club so people can't get out which then catches on fire and kills everyone), and ordinary negligence (securing a heavy thing in the air with just a knot that falls and kills someone). Even if someone "should have known," that is almost never enough for criminal liability.
Thanks I know, I said that I don't know the specifics and that others (lawyers) will have to decide on that.