I will pose the question directly to you then.
What would YOU do if someone showed enough emotional instability (perhaps due to life events and changes) that you earnestly believed that your friend posed an iminent hazard to them self or perhaps others?
Or would you do nothing and then after he does something terrible sit back and say that you know something like this would happen?
Serious question.
At what point do you intervene or get help with intervention?
Bad things happen. Some are predictable. That does not mean that we should act to prevent all potentialities. To do so destroys Freedom, which is worth far more than a few million lives. Just ask the millions who have given their lives to protect and promote freedom. Personally, I'd take the opinion of one who gave their life for Freedom before I'll take the opinion of those who think that people should be punished before they do something bad.
That person who is exhibiting signs... might just right themselves... avoid the temptation... find Christ... might get distracted by a shiny object... or anything else. Allowing government to start acting against those who merely "show signs" simply invites them to open those interpretations... as they ALWAYS do... and literally invites the worst authoritarian state you can imagine.
Cripes, every male child between the ages of 8 and 18 (okay, 28) exhibits signs of pyromania, tendencies towards physically violent reactions to physical challenges, an amazing propesity towards nearly-uncontrollable lust towards attractive females, etc. Shall we lock up all the boys now?
I call the person’s immediate family and/or I call the authorities if an individual is talking of suicide or hurting others.
If an individual of any sort pulls a gun and starts firing into a crowd, I hide behind whatever I can and start squeezing off rounds into the perps body no longer moving. This is common sense.