A man awaiting execution in Texas for a cold-case killing in Oklahoma pleaded guilty to additional murder charges Wednesday.

William Reece, 62, pleaded guilty in a Galveston courtroom to killing 12-year-old Laura Smither of Friendswood and 17-year-old Jessica Cain of Tiki Island. Later Wednesday, in nearby Angleton, he pleaded guilty for the disappearance and death of 20-year-old Kelli Cox of Denton. All three had disappeared in 1997.

Each guilty plea carries a life sentence.

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In 2016, while serving a 60-year sentence for a 1997 kidnapping, Reece began cooperating with the investigations of the other cases.

Laura Smither had gone for a morning jog in Friendswood in April 1997 and failed to return. Her remains were found more than two weeks later, about 30 miles away, in a retention pond near Pasadena.

Jessica Cain went missing in August 1997. Her car was found abandoned on Interstate 45 near Tiki Island, a community across from Galveston Island. In April 2016, Reece led investigators to a pasture south of Houston, where they found Cain’s remains.

Investigators also found the remains of Kelli Cox at the site. Cox was a University of North Texas student who was last seen in Denton in 1997. Reece faces a capital murder charge in Brazoria County for the killing of Cox.

Reece was convicted and sentenced to 60 years for the May 1997 kidnapping of Sandra Sapaugh after he abducted her in Houston by pretending he was going to help her fix a flat tire. Sapaugh was able to escape by jumping out of his truck on Interstate 45.

He has been on death row since last year, when he was sentenced for the 1997 killing of 19-year-old Tiffany Johnson of Oklahoma City, whom he had abducted from a nearby carwash.