Do you think the Uvalda shooting was planned?

I hate to think that, I really try not to buy into conspiracies and really I don't believe that anyone besides the shooter planned it out. It just seems so weird how everything worked out. School's are supposed to be locked down and impossible to enter from the outside. But a door just happened to be unlocked and it just happened to be the door that the guy went into. And the cops could have stopped him, but stood around for over a hour waiting and stopping others from going after him. Sounds really fishy to me.