"Guards, evacuate the surrounding area and let everyone know to stay inside!"
"And close everything up as much as you can! Let's see what this is..."
To the group, much quieter
"This reminds me of a story where an attacker created an obvious distraction that had nothing to do with the real attack. In the story it was a forest nearby that was used with trees swaying, strange lights going up and down and sounds and screams coming from it without any obvious threat to the fort. But it was an interesting spectacle so guards focused their attention there. In the meantime from the back came a stealthy team that managed to enter the fort before the alarm sounded.
We might want to run by that gnomes shop, just in case."