Malice + stupidity would answer this one.

I think that's the impression intended to be given in the hopes of having a chance to fight the case.

Agreed, to me even a term like "negligence" seems to lean too far into accepting it all as mere "mistakes". They way he talks about it in interviews, he makes it sound like he was a child operating a handgun, and while he doesn't remember how it all went down, he's very sorry bad things happened.