1. yup.1. He couldn't have known he had CTE. That's only a diagnosis that can be made post-mortem, as far as I know.
2. He might have had other mental problems, which he interpreted as being CTE. Perhaps schizophrenia or some form of paranoia.
3. It's possible he had CTE but I think CTE is exceedingly rare for people who stopped playing football in HS. I could be wrong about that.
4. It's also possible that he decided to kill himself, but wanted to take out somebody bad with him -- and maybe he had a friend with a CTE like condition. Or just going by media reports. Maybe his favorite player was Aaron Hernandez -- something like that.
2. Definitely.
3. No one really knows the rate of CTE for high school because so few cases are autopsied. Most kids who commit suicide don't get their brains sent to Boston U.
4. I'd go with No. 2. He was mentally ill, and that mental illness caused him to go down the CTE rabbit hole.