FARGO - A drug dealer who executed a man in a dispute over 5 pounds of methamphetamine must spend the rest of his life in prison to protect the public, a federal judge says.

Gabriel Martinez, 30, was sentenced Friday on federal murder and drug conspiracy charges in the 2005 death of Lee Avila, who was shot nine times in front of two small children in an East Grand Forks, Minn., trailer home.

"He (Martinez) knew the kids were there. He knew it. But he did it anyway and then he brags about it," Assistant U.S. Attorney Chris Myers said of the murder. "A sentence of anything but life in prison would be an act of mercy."

Defense attorneys asked for a sentence of 30 years, which was the mandatory minimum. U.S. District Judge Ralph Erickson said the fact that children were forced to witness the murder and that Martinez later tried to coerce two prison guards into helping him escape were factors in his decision to hand down a life sentence.

"I'm more concerned about Mr. Martinez than any defendant I've ever seen," Erickson said.

Authorities said Martinez shot Avila in front of Avila's 4-year-old niece and the 9-year-old son of Avila's girlfriend. Before he was sentenced, Martinez apologized to the children and the families of all the people he pressured into a drug conspiracy that federal authorities dubbed Operation Speed Racer. It led to charges against 50 people.

"I took a man's life and that's something no man had a right to do," Martinez said.

His attorneys argued that Martinez was only following orders of a drug cartel whose motto was "kill or be killed," and said he tried to force Avila out of the trailer home and away from the children.

"The victim was, in fact, a drug dealer," said Marlo Cadeddu, a defense attorney from Dallas. "There's a difference between the murder of someone who is a drug dealer and someone who is a complete innocent."

Martinez was one of five people convicted in Avila's killing. Jorge "Sneaky" Arandas, the leader of the drug conspiracy, was sentenced to 40 years in prison. Michael Petzold, Martin Carrillo and Alan Wessels, who went to East Grand Forks with Martinez, pleaded guilty to helping with the murder. Wessels was sentenced to 23 years in prison and Carrillo to 20 years. Petzold is awaiting sentencing.