So let's say you leave your facebook logged in and fall asleep. Then your ass-hole kid brother comes in and plays a prank by posting something on your feed that could be construed as violent or terroristic? You can't ever buy a gun again?
It's not outrageous that it should be looked into. If it was just a prank, well they won't be google history researching school shootings, for example. A nutjob doesn't just make one shitpost and then go into hiding, he leaves a trail. A shitpost saying "Ima kill kids" might just be enough to have a look into, just to see if it's a habit.