The vampire's normally flawless aim was being impaired by both the bleeding slashes on his chest and the blow to the back of his head, thus causing him to miss the first time. He wasted no time in reloading the gun, taking aim again at the now steady target provided by Katara's blood-bending and Sarah's stability. Of course, Angel was unaware of the details of both those factors, let alone the blonde woman's name, but that didn't matter at the moment.
What did matter was taking Oz down in a way that didn't end in his death. The last thing Angel needed was to be responsible for the fall of another friend. That had happened far too many times than he'd like to admit.
Pulling the trigger, the gun fired, landing a dart full of slayer tranquilizer in the werewolf's neck.