“Error’, my arse.
They were somehow tipped off in advance.
Needs to be fully investigated, and one just might find a solid tie back to some of our communist “friends”.
Send them to Guantanamo Bay. They’ll tell who tipped them off.
And it was also an “error” when LBJ aide Bill Moyers (late of PBS) instructed the Secret Service to remove the bullet proof top from the Presidential limousine in Dallas.