I mean, it’s not. You could also mention the fact that a building with such an obvious sight line wasn’t secured, that people saw him up there 15 minutes before it happened, and secret service told them it was nothing when they warned them, or that 8 secret service agents (the best of the best) apparently couldn’t keep one 78 year old man under them (their main objective), and he managed to over come those 8 officers for a perfectly positioned camera.