I can't blame the guns, they are inanimate pieces of metal, and as soon as he took them out of the house they became illegal guns even though they were purchased legally. I just can't understand what happens inside the head of someone to make them do something that heinous (and that's a weak descriptor). He killed his mother first, by itself, an unthinkable act. Then he went to the school. Maybe some insane jealous rage over the kids she taught? All I can really say is that I cherish my kids and grandkids a little more than I already did.
