If someone is a danger to themselves or others CALL THE COPS.
Then and there. Done, the problem is not yours any longer.
I promise you, you are doing everyone involved a favor.
Don't worry about what will happen to the individual.
The worst thing that could happen would be an untreated individual with symptoms of schizophrenia spending a night in jail instead of on the streets.
The best case scenario is they receive treatment, medication, and as most cases return as kind, caring, loving individuals who are non-violent.
Most ppl w/ schizophrenia are awesome ppl when treated, after receiving the proper help they need, and are no longer violent.