The Quest of Isaac O'Connor [Unfinished]

The spirit is moving too fast, and you don't have a clear shot. You end up accidentally shooting lightning beside the fleeing spirits, which makes them skitter to the side. Luckily, the other spirit wasn't expecting them to change course and zooms right past them. Now, it's between you and the spirits, and it takes a moment to decide who to go after. What do you do?