Shooting the hostage holders dead if the life of the hostage(s) is/are threatened is a standard SWAT tactic. Shoot to kill authority came from the White House, by the way -- the President left it up to the officers on the spot to deal with it in what they thought was best.

According the my wife, the "Washington Post" reported that all of the crew had training in how to act in a piracy situation and they did as they were trained.

As for unarmed -- well, a ship is full of potential weapons and always has been. Fire axes, butcher knives and cleavers in the galley, lengths of chain, even fire hoses and CO2 extinguishers. What is needed is the training to react to a surprise (and this wasn't: "...the pirates are closing in") and the will to use the weapons at hand.

Pirates are not in it for blood, they're in it for money. They can't sail the big ships to a port and need the crew for that, so I doubt that this will result in more pirates shooting.

First the French, now the US. I hope that the message is getting out.
"Millions for defense but not one penny for tribute," as Robert Goodloe Harper said regarding the XYZ Affair in 1798.