A technical explanation and documentation demonstrating that websites made as a 'tribute' to the victims of the Sandy Hook massacre, were actually uploaded and online before the attack. This means that somebody knew the attack would happen in advance. Note also that one eyewitness says (on video) that police arrived BEFORE the shooting started.
While 9-11 was happening, believe it or not, the Pentagon was performing a drill/exercise on what would happen if an airplane was rammed into the Pentagon. Son of a gun - what are the odds of that! Turns out, much of the violence meant to steer our society happens in just that way... drills that magically morphs into real-life. You'd have to be a real die-hard coincidence theorist, to believe that these are all "accidents".