A no-win situation for the plant personnel, had they fired the article headline would have read:

NUCLEAR PLANT SECURITY PERSONNEL SHOOT POLICE

Somebody happened to catch the state police markings quickly.

Now, they could have been stolen or falsely marked helicopters intent on landing hostiles inside the protected area. So it really is a conundrum. Should they have fired or not, this time it turned out to be “good guys” in the helicopter, but what about next time?

[edited to typo a correct]