A Missouri man pleaded guilty Thursday to capital murder for killing a pregnant woman, her husband and son at a Texas Panhandle farmhouse in 2005.

Levi King, 26, entered his plea in Lubbock and then prosecutors began the punishment phase. The state is seeking the death penalty.

King pleaded guilty to killing Michell Conrad, 35, her husband Brian Conrad, 31, and her 14-year-old son, Zach Doan. They were found slain in their remote farmhouse. Michell Conrad was six months pregnant.

Her 10-year-old daughter survived and called 911.

Texas law enforcement officials did not released the 911 tape, any details about how the girl survived or what she might have seen. It was not clear whether she would testify. Authorities have never released a motive for the slayings. Earlier this year, the judge in the case issued a gag order.

King pleaded guilty last year in the shooting deaths of Orlie McCool, 70, and his 47-year-old daughter-in-law, Dawn McCool. Their bodies were found by a relative in a rural Pineville, Mo., home on Sept. 30, 2005 — the same day authorities in the Texas Panhandle discovered the bodies in the Conrads' home.

Missouri authorities said King drove Orlie McCool's pickup truck from Missouri to the Conrads' home in Texas.

King was caught the same night trying to re-enter the U.S. at the Mexican border in El Paso, Texas.

Shortly after investigators brought the truck back to Missouri from El Paso, a name tag with Brian Conrad's name was found in the vehicle.

Investigators said ballistics tests linked one of four guns found in the truck to the Texas killings.

King was sentenced to two consecutive life terms without parole for the Missouri killings. The Texas punishment would take precedence under an agreement with Missouri.