Editing Warhammer 40,000/Tactics/Kill Team(8E) Guide and FAQ (section)

===Who can I attack?===
====My model successfully charged====
You can only direct your attacks against enemy models that your charge move brought you within 1" of. This means that even though you chose both models A and B as targets of your charge, your charge move got you within 1" of model A, and your pile in within 1" of model B, you can only direct attacks against model A.

Does that mean if I charge two models into a single enemy model, and the first kills it, my second model can pile in against a different enemy model, but not attack it?
Yes. This ruling also makes fight twice abilities a lot less useful.

====My model was charged successfully====
You can attack any enemy model that is within 1" of your model after your Pile in move.

====My model ended up within 1" of an enemy model====
You can attack any enemy model that is within 1" of your model after your Pile in move.