What type of kid would want his parent dead after receiving a spanking?

I'll be very brief. My young 10 year-old nephew has been displaying aggressive and disruptive behaviors for nearly 2 years. He got suspended once for pranking a classmate with a dead rat. My aunt and uncle sometimes spank him but just when things have gotten better, they received another new complaint from the teacher a couple weeks later or so.

3 months ago, my uncle spanked him with a strap, then made him apologize after he tried to deliberately set a relative's barn and car on fire. He already lit the matches. He seemed to have apparently changed afterwards and his behavior was supposedly getting better. That's what we all thought.

Fast-forward to recently; my uncle has been having diarrhea a couple times. What they found on his Internet searches and private notes on his drawer was horrible. He was searching about laxatives and its effects, names of undetectable poisons, Mary Bell case, how to cry at a funeral, etc. On his notes it was about possible ways of getting rid of his dad (my uncle) and lying by making it look like an accident or self-defense and how the laxative on his food is just the beginning. He was basically pretending to have learned after the strap spanking but it was all an act.

My aunt and uncle are obviously getting in contact with a professional at this moment. I've never heard of a child with that reaction after getting spanked. This is indeed disturbing. What would you do if you discover your child wanted you dead and even food posioned you, at that young age? I know my uncle isn't perfect and maybe spanking isn't the answer but wanting your own father dead is too far. What type of kid would want his parent dead?

Updates
11 mo
My uncle was literally in tears after reading all that.
What type of kid would want his parent dead after receiving a spanking?
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