Admittedly, it's been a while, so I could most certainly be wrong, but the signs contained a lot of text, stating this was an air traffic control facility where operations are critical, disruption to operations could result in serious injuries or loss of life, etc. Kind of a "please don't do anything bad, people could get hurt" type of warning.

If they were referring to trespassers, I would have expected some sort of a "use of deadly force authorized" warning, like I've seen near the presidential aircraft hangars at Andrews AFB. But I wasn't paying close attention, I may have missed them.

The gate guard may certainly have been armed, I just meant I didn't see any overt security display (patrolling guards, etc.)

Regardless, I for one am in full support of shooting anyone that would attempt to monkey with ATC operations, signs or not!