Are you familiar with NAMI? If not that could be a good resource for finding the best ways to help your brother and get support you may need, https://www.nami.org/

I haven't experienced full blown psychosis but have had a mental health crisis that resulted in police involvement and hospitalization. Looking back it would've been much better if I had been able to work on a plan with someone for what I myself would do in a crisis situation and how others may or may not be involved.

That said, early on I may not have been willing to create a plan with someone or able to acknowledge the seriousness of my situation enough to make my own plan. It sucks but there's a good chance you might not be able to help directly when he's most vulnerable.