The way the story was told to me, it portrayed Junior as doing it on purpose. I do seem to remember he had a reputation for bad behavior beyond offing Patrick.
Junior was definitely a liability to little curious hands, which every pre-teen girl has in regard to horses.
However, you are very likely right that he was probably restricted as to who was ALLOWED to work with him, not who was CAPABLE of doing so.
I also am acquainted with a horse that did stuff like that. He is one of the horses who dumped me on purpose. He also tried to stomp on me a couple of times and charged me in the pasture -- I had to bounce a bucket off his nose to get him to leave me alone.
My trainer bred him - he was the product of her old Tbred stallion (who was a WONDERFUL horse - she didn't let the little kids handle him but they would have been perfectly safe on him or around him) and one of her warmblood mares (I have ridden her and she's a little hot but not vicious at all and a sweet mama.) He just turned out bad. Not too long after he dumped me and kicked somebody else, she sold him to an experienced rider to train for 3 day. He was absolutely beautiful and an extremely athletic and talented horse, but he had a screw loose.