I'm going to call out a person with mental issues
Why would you call them out?
I've met them a few times and they get on my nerves.
If there they have mental health problems you should rethink yelling at them. It may produce more harmful results than you being annoyed, like harm to them or yourself.
What if I just yell and then walk away.
Even if you prevent harm from coming to yourself, that doesn't mean you won't potentially cause the other person harm.  You don't want to add extra problems for a person already struggling with that sort of condition, do you?