The Sleep and Deep Slumber spells wreak havoc on the militia, disabling them at an alarming rate; not that there were many to begin with, given the small size of the town, and the lack of warning they'd received.  People were quickly packing up and fleeing their homes, but were never going to get beyond the borders of the town, given the speed the mounted raiders are advancing, flaming arrows raining down on the town, lighting the buildings on fire, as people start screaming and beginning to run.