We don't know what the LEO did or didn't do. We know the building wasn't secured, this guy had a solid plan of attack, and Trump wasn't pulled. There is no sauce on the details of the radio comms yet. The sniper physically did not have a target until the shooter got his head up over the ridge of the roof he was on at which point he started shooting and was hit within seconds. There is no sauce showing that the sniper had a clean shot and waited.