ES
Looking at the Pictures and the signs, then at least one of them would most certainly have the potential to cause more than a headache for an hour or two to the whole site.
Lights? what lights, pass the torch please may become the statement of the day/night/week...
Barnstormer is right, Security is THE question here, they should not have been able to get in, much less wander about for a period of time without challenge. Security is not just the job of the barrier operator on the gate, it is the responsibility of EVERYONE on base and that includes both Service and Civi, if it looks out of place either challenge (service people get to do this) or report, either way don't ignor.