Scott & Jean Adam and Phyllis Macay & Bob Riggle

Prayers and condolences to their families.

(CBS News) — The four Americans aboard a yacht hijacked by pirates off the coast of Somalia are dead.

Hijacked last Friday off Oman, the Quest was being piloted toward the Somali coast — and was being shadowed by a U.S. Navy warship.

CBS News national security correspondent David Martin reports that gunshots aboard the yacht were heard, and the warship took action.

All 4 Americans were dead, killed apparently by their captors.

There were more than a dozen pirates on board, some dead and others captured, Martin reports.

The Americans were Scott Adam and his wife, Jean, of Marina del Rey, Calif.; and Phyllis Macay and Bob Riggle, both of Seattle.

Adam, in his mid-60s, had been an associate producer in Hollywood when he turned in a spiritual direction and enrolled in the seminary a decade ago, Professor Robert K. Johnston of Fuller Theological Seminary in Pasadena and a friend of Adam’s, told The Associated Press.

“He decided he could take his pension, and he wanted to serve God and humankind,” he said.

Since 2004, the Adams lived on their yacht in Marina Del Rey for about half the year and the rest of the year they sailed around the world, often distributing Bibles in remote parts of the Fiji Islands, Alaska, New Zealand, Central America and French Polynesia, Johnston said.