Rex calls out to Duglan.
Wait, don't scare him off.
He follows the gnome to the door, speaking in halting Gnomish.
I am sorry I shot you. I thought you were a bad man. Take this healing potion.
Rex takes out a potion of Cure Light Wounds and places it on the floor, then steps back so the gnome can take it without getting too close.

Spoiler
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Diplomacy check to get the gnome to stay and pick up the potion:(1d20+1)[9]