Someone got the axe or was sequestered in DC within a very short period of this occurance. Someone can probably noodle that person out. They had to be pretty well placed to know time and route.
Be interesting to learn if the POTUS consented and, or just, AF1, was utilized as bait to smoke out the traitor that gave clearance to this! He would gain massive hit points and loot of badassery!
But where was the President going on June 10th?