Double Tap

Dexterity 13, Rapid Shot.

When using a double crossbow or repeating crossbow with at least two bolts loaded, you may shoot two bolts as a single attack. This attack suffers a -2 penalty to the attack roll but deals the crossbow’s normal damage twice on a successful hit (so a +1 light double crossbow with the flaming enhancement would deal 1d8+1+1d6 fire damage twice). Critical hits, sneak attack damage, and other precision-based damage apply to only the first bolt.

You can only shoot a single bolt with each attack.