Four Americans taken hostage by Somali pirates off East Africa were shot and killed by their captors Monday, the U.S. military said, marking the first time U.S. citizens have been killed in a wave of pirate attacks plaguing the Gulf of Aden and the Indian Ocean for years.

U.S. naval forces, who were trailing the Americans’ captured yacht with four warships, quickly boarded the vessel after hearing the gunfire and tried to provide lifesaving care to the Americans, but they died of their wounds, the U.S. Central Command said in a statement from Tampa, Fla. Two pirates died during the confrontation and 13 were captured and detained, the U.S. Central Command said. The remains of two other pirates who were already dead for some time were also found. The U.S. military didn’t state how those two might have died.

On Monday, two pirates had peacefully come aboard the USS Sterett to negotiate with naval forces for the release of the hostages, and remained aboard overnight.

But on Tuesday, pirates aboard the Quest unexpectedly fired a rocket-propelled grenade at the Sterett. Shortly afterward, gunfire erupted inside the Quest cabin, and U.S. special forces responded, approaching the Quest in small boats and boarding the vessel, Vice Adm. Mark Fox, commander of U.S. Naval Forces Central Command said in a Tuesday press conference.

Some pirates moved to bow and put up their hands in surrender. The U.S. forces killed two pirates in the course of clearing the vessel – one with a handgun and one in a close-combat knife fight. There were no injuries to U.S. forces or damage to U.S. ships, Fox said.

The Quest was the home of Jean and Scott Adam, a couple from California who had been sailing around the world since December 2004 with a yacht full of Bibles. The two other Americans on board were Phyllis Macay and Bob Riggle, of Seattle, Wash. Scott and Jane Adam documented their maritime missionary work on their website, S/V Quest Adventure Log.

This story seems to be missing something…..perhaps a rescue attempt gone awry?