Yes, denying a constitutional right is a dicey area, especially if no crime was committed previously. However if the person is involuntarily institutionalized / it can be proved that they've made threats against others, then I think that this should be a no brainer. Red flag laws are crap, but this goes beyond those. It's a little hard to believe that they didn't intentionally let this happen, but "never attribute to malice what can be explained by stupidity."
I don't even trust the cops though and I'm fuckin' mayo on white bread white. I can only imagine being some other ethnicity in this country.