The four Americans aboard the yacht Quest that was hijacked by Somali pirates have been killed. U.S. troops had been shadowing the vessel stormed aboard early Tuesday after they heard gunfire. They discovered that all four hostages had been shot by their captors. Two pirates were killed in the clash, two others were discovered previously dead, and 13 were captured.

The Quest was hijacked on Friday off the coast of Oman. The vessel was owned by Scott and Jean Adam, from California. The two other Americans onboard were Phyllis Mackay and Bob Riggle. The Adams have been sailing around the world since 2004 distributing Bibles to schools and churches in remote villages in areas including the Fiji Islands, Alaska, New Zealand, Central America and French Polynesia.

Somali pirates currently hold 30 ships and more than 660 hostages. They took the Quest two days after a Somali pirate was sentenced to 33 years in prison by a New York court for the 2009 hijacking of the Maersk Alabama.

Pirates demand and often receive multimillion-dollar ransoms and have increased attacks off the coast of East Africa despite an international flotilla of warships battling the problem.

“God, we pray for the families of the Scott and Jean Adam and Phyllis Mackay and Bob Riggle. We pray for comfort. We ask too that this horrible blight of piracy will be stopped. Intervene, God and break this terror. Give wisdom and courage to those fighting the pirates. Increase pressure in and on the pirates themselves. Transform this situation. Free the remaining 30 ships and 660 hostages. In Jesus’ name.”