You do the best you can. A gun is an extraordinarily convenient and efficient killing machine. Statistics show both its ubiquity and lethality with respect to suicides.
It is bogus to suggest that because you cannot solve every problems you shouldn't try to solve one.
All of those suicides, homicides, and mass killings have one thing in common. On the end of whatever is used to perpetrate them, from a burner phone setting off a bomb to a slasher attack in the subway, to some jerk shooting up a concert, or a drive by at a block party, each one of those incidents or events has a person who is NOT normal attacking others, or themselves.
In the meantime, there are people using similar devices all around the world with neither attempt nor intent to harm others, and without doing so. The devices are not the problem, counselor, though banning everything might seem like an easy fix.
Cain smote Abel with a rock. Are you going to ban rocks? (Lay off, d@mnit, I'm a pro!)
Instead of turning the world into a padded cell, how about we gather those in need of help and put them in an environment where they can get that?-- while the rest of humanity goes on living, with their stuff intact.