Complex sentence: To kill the moose, they would injure it first, by using a bow and arrow or other weapons, and after it was down, they would move in on it and finish it off with spears and their dogs.
Split into simpler sentences: To kill the moose, they would injure it first, by using a bow and arrow or other weapons. After it was down, they would move in to finish it off with spears and their dogs.