The drones at Langley weren't shot down either.
They were not only unidentified, but NASA sent a NASA WB-57F aircraft up to Langley to find out what the hell was going on.
The fact that this aircraft--a NASA WB-57F--was seen flying circular orbits centered around Langley AFB suggests that it was involved in a specific mission or investigation, possibly related to the drone swarm or other aerial phenomena observed in the area. The WB-57F's capabilities would allow it to gather detailed data that could be useful for both NASA and the U.S. military, particularly in understanding or monitoring unexplained aerial activities.
Key point:
If our military can’t stop drones from overflying sensitive installations (let alone identify the operators)...
...then NOTHING will stop a serious assassination attempt.