> 17 years old is not a "kid". That's a young adult.

Try telling that to the military.

> The police do not control the mental health system.

That doesn't mean they don't play a role in how society deals with mental health.

> Not based on what we know.

We know humans have free will.

> The police must react if that person is threatening the life of another.

False. Police have no legal obligation to endanger themselves for the protection of others.

> but so far there are no red flags.

Just newly red walls and carpeting.