Gaining pain tokens mid-assault phase

Had this situation today

An Incubi squad led by an archon already has a pain token (yay drugs) and assaults a marine squad containing a marine librarian. The archon kills the librarian at his int step with his husk blade and the unit gains its second pain token. Do the Incubi gain the benefit of furious charge when they strike the marine squad at their (lower) int step or not?

The unit does have two pain tokens and it did charge into assault in the current turn.

Pain tokens come in to play at the end of the phase

Yeah, I forget where this is - was it in the FAQ? - but what DominicJ says is right I'm afraid.

It is indeed in the DE FAQ.