human
I remember the guy that shot a bunch of people from a bell tower in 
Texas on a college campus. They found he had a brain tumor that they believe now was the cause of his violence.
This guy seemed to have planned it out. They may never know why he did this. Sometimes we never know what motivates a person to suddenly kill a bunch of fellow human beings.  
Maybe he wanted to "out do" his father and be a bigger, meaner bad ass.
gpt
{"moderation": ["toxicity"]}