For me, any attack or act of piracy against a US flagged vessel would constitute an act of war. The pirates involved would be captured and if an innocent was killed, the pirates would be executed at sea, their bodies would be returned to their host nation. Any vessel that hosted or aided the pirates would be sunk. The host country would be made to pay retributions to the families of the victims and or companies affected.
I realize this maybe an extreme solution but at this point what do we have to lose? How many more innocent people need to suffer or be killed before we decide to act?