Benton County added a life sentence to one already handed down by Multomah County earlier this week for a carjacker who killed two men and a teenage girl two years ago.

Shawn Womack, 23, sat quietly under heavy guard and in shackles as Circuit Judge Janet Holcomb im-posed the sentence, part of a plea agreement with Multnomah County.

The Benton County sentence of life without parole will run consecutively with the Multnomah County judgment, assuring that Womack will die in prison.

“The sentence stands alone,” said Benton County District Attorney John Haroldson. “If something were to happen in the other cases, this would not go away.”

“He waived everything that could be waived in order to get some finality in this,” Haroldson said.

Womack admitted killing Chai Taphom, 28, Michael Burchett, 38, in separate Portland carjackings in May 2006. He then executed 17-year-old Marissa Manwarren, the girlfriend of an accomplice, in rural Benton County after she had learned about the murders.

Haroldson said he did not seek the death penalty because Womack was remorseful and confessed right away, which helped police locate Manwarren’s body and that Womack was willing to cooperate in negotia-tions with both counties.

Womack planned robberies with his girlfriend, Jasmine Lesniak. Both were students at Linn-Benton Community College in Albany.

Womack admitted he had threatened to kill his accomplice, Cevelino Capuia and his pregnant 17-year-old girlfriend, Manwarren, if they told anybody about the two carjackings and murders.

After Capuia was arrested, Womack and Lesniak picked up Manwarren, apparently to give her a ride, but Womack instead drove to Benton County, shot her and drove to the Oregon coast near Newport to dump the body.

Capuia and Lesniak face multiple charges in the case.