A federal judge on Monday ordered 12 life sentences for a Somali pirate negotiator involved in two hijackings that saw four Americans killed.

Mohammad Saali Shibin was convicted on 15 charges including hostage-taking, kidnapping and weapons offenses linked to the pirate seizure of a German cargo ship in 2010 and an American sailboat in 2011 in the Indian Ocean.

"To me, nothing could be more heinous than to take unsuspecting people... and just shoot them," U.S. District Judge Robert G. Doumar said during the hearing. He said the life terms were "what I'd consider a light sentence." Prosecutors did not pursue capital charges.

During the trial, prosecutors said Shibin received $37,000 for acting as a hostage negotiator after Somali pirates held the cargo ship Marida Marguerite for a $5 million ransom in 2010.

In 2011, an American yacht and its four occupants were seized. After the Navy began shadowing it, a pirate fired at the military vessel, and the hostages were killed by their captors before Navy SEALs could board.

The slain Americans were yacht owners Jean and Scott Adam of Marina del Rey, Calif., and friends Bob Riggle and Phyllis Macay of Seattle. Some of the victims' relatives attended Monday's hearing.

"Today's sentencing should send a clear message to pirates around the world that you can run, but you can't hide," U.S. Attorney Neil MacBride said after the hearing. "The U.S. government will find you."

MacBride said Shibin was ineligible for parole: "Mr. Shibin will die in a federal prison."

Shibin also was ordered to pay $5.4 million in restitution.

Defense attorney James Broccoletti said in an interview that Shibin did not fit piracy charges because he hadn't been on the water with the crews that seized the vessels. Broccoletti said he would appeal Shibin's case to a higher court.

But Doumar said repeatedly that he viewed Shibin as "part and parcel" of the piracies. Shibin, Doumar said, used the threat and fact of torture of the German crewmen to extract a higher ransom, and was present during the brutality.

"You joined the conspiracy, knowing exactly what was happening," Doumar said. "You had a gun, you guarded, you were there... and you received a substantial amount of money."

"I think you're lucky not to be facing the death sentence," the judge said.

By Steven Vegh