You said he was taking massive testosterone. Why? Is this true?
He was taking testosterone to counteract the listlessness caused by dementia and his Alzheimer’s meds. Along with “uppers”, probably adhd meds or Modafinil.
All of that is fine and actually good in moderation, but higher doses cause the weird aggression he had.
Testosterone will also cause prostate cancer (if hormone sensitive) to rapidly spread. This is why older men on replacement hormones get routine PSA checks.