When a local Deputy showed up over at a friends' place (amicable visit, not business) he was wearing a bullet proof vest. It was the first time we'd seen him in one, and my friend just quipped " Dammit, K____, you know that thing is going to make them go for the head shot. "
We all got a laugh out of that, the Deputy included, but taking guns from someone who may be suicidal just limits their options, it doesn't change the problem.
If they want to go out in a 'blaze of glory' or 'get even' with people they blame on their way out of this existence, they will find another way, possibly one with even more 'collateral damage' than whatever they'd planned.
The bottom line question is: Is this effective at reducing mass casualty events? Is this effective at reducing murder suicides? Are there any real number events, with baselines, that can demonstrate actual benefit (not just benefit versus some projection, because we've seen how those work with climate).
Are those troubled people getting meaningful help if they need it? Is this, where practiced, actually working? (aside from using this as a political tool to oppress people TPTB don't like)?
The whole idea of Minority Report style policing without so much as a psychic prediction of violence, is repugnant, and downright unconstitutional. Even more dangerous is the idea that the people who decide who is a risk might not know nearly as much as they think.
Taking someone's guns away might be the event that pushes them beyond their limits of endurance for all the ills in their life, after all.