Vetting

This question is for people who has trained others.

For context, I live in the Biblebelt where treating gays and transpeople like humans makes you a 'radical leftist'... (I'm not. I consider myself more a libertarian.) Regardless, it's safe to say those types are not welcomed at most gun spaces here so I've had a few come to me to learn about guns. I was pretty excited that my eccentric hobby might be used for a good purpose and I probably should have thought this through more. I even started to take Firearm instructor classes so i could start doing legit classes. But then I found out one of them has attempted suicide like 3 times. I started asking questions and found that several had. I don't say this to reinforce negative stereotypes... these people are harassed constantly here, of course they're depressed or worse.

So here is my conundrum... if I teach someone how to use a firearm and they kill themselves with it I'm going to feel like shit. But, if I refuse to teach someone and they get kill in a hate crime I'm also going to feel like shit. How do you vet people? Where do you draw the line?

Edit: A lot of you are missing the point of this post. The question is how to vet and where to draw the line. Most people will not openly admit to being suicidal and it's not like I access to their medical history. I didn't know until a family member came to me and provided very person information. That particular person is no longer being taught by me but how do I find out in the future? Where do you draw the line? Actual attempts? Depression? Dysphoria?