All four American hostages on a yacht taken by pirates off Somalia have been killed, the US military said.
Negotiations had been under way to try to win release of the two couples on the pirated vessel Quest.
Gunshots were heard. When US forces reached the yacht, they found all four hostages had been shot, US Central Command said today.
The Quest was the home of Jean and Scott Adam, a couple from California who had been sailing around the world since December 2004.
The two others on board were Phyllis Macay and Bob Riggle, both from Seattle, Washington.
Central Command said negotiations had been under way to try to win their release.
"We express our deepest condolences for the innocent lives callously lost aboard the Quest," said General James N. Mattis.
Two pirates died during the operation, and 13 were captured and detained.
The remains of two other pirates who were already dead also were found. In total the US said that 19 pirates were involved in the hijacking of the Quest.
Only minutes before the American deaths were announced, a Somali pirate told The Associated Press news agency by phone that if the yacht was attacked, "the hostages will be the first to go."
"Some pirates have even suggested rigging the yacht with land mines and explosives so as the whole yacht explodes with the first gunshot," said Abdullahi Mohamed, a friend of the pirates holding the four Americans.
Graeme Gibbon-Brooks, the head of Dryad Maritime Intelligence, said he was confounded by the turn of events.
"We have heard threats against the lives of Americans before but it strikes me as being very, very unusual why they would kill hostages outright," he said, adding that the pirates must have realised that killing Americans would invite a military response.
The military said US forces have been monitoring the Quest for about three days, since shortly after the pirate attack on Friday. Four Navy warships were involved, including an aircraft carrier.
Last week a Somali pirate was sentenced to 33 years in prison by a New York court for the 2009 hijacking of the Maersk Alabama, a US cargo vessel. That hijacking ended when Navy snipers killed two pirates holding the ship's captain.