Just some random thought I had in the bus today:
Apollo is often named "Death-bringer", "of deadly arrows" and is seen as an active God on war. This of course correlates with the slaying of the Python, plague-bringing, and the likes; but it is also in a very war-like (or Ares-like, Athena-like) kind of death bringing.
I just realized how well this connects with another facet of him: the transition between adolescence and manhood - Apollo is the God of this initiation, just like His sister is for girls. This passage marked the entrance of a boy into the world of men which, coincidentally, is the world of war, which means that one facet of growing into manhood is war and therefore he would be death-bringer in this way as well.
Like I said, just some random thought which needs a lot to be developed upon.