The original Core Rule Book rule is "aiming" (+1 DM on 'to hit' per minor action with a maximum of +6).
"Aiming for the kill" came soon afterwards in Mercenary (+2 to damage per minor action aiming with a maximum of +6, i.e., maximum of 3 minor actions).
It's fairly clear from the wording of "Aiming for the kill" that it is a special case of aiming and that the aiming 'to hit' bonus is not included. That is, they should be considered as completely separate tasks. Thus, you can't aim for 6 minor actions (not shooting at the end of it) and then aim for the kill for 3 minor actions, finally shooting once and getting +6 to hit AND +6 damage.
i.e., per squeeze of the trigger you can EITHER aim (to hit bonus) OR aim for the kill (damage bonus) but NOT BOTH.