What if your kid develops a mental disorder at the age of 18 or 20?
This type of thing happens out of nowhere.
I have family members and friends who were suicidal at some point. Other friend developed paranoia at the age of twenty something.
We never know, because we are human beings. Human beings are fragile and unpredictable.
If everyone has access to guns a disaster is bound to happen if a person develops a mental disorder. Which is not that uncommon.