When after an actual shooting, it its found that the shooter has, at some point in his life, made a post on social media that one could - if so inclined - inter

When after an actual shooting, it its found that the shooter has, at some point in his life, made a post on social media that one could - if so inclined - interpret as an announcement of what he was about to do, people will go absolutely mad screaming: "Why did they not arrest him beforehand???!?!?!?!!!" This must be exactly what those screamers are envisioning...