Lawyers for a Brownsville death row inmate filed a motion on Thursday to challenge whether he's competent to be executed. They submitted the filing about two hours before the deadline.

John Allen Rubio is one of the Rio Grande Valley's most infamous killers. He's set for execution in November 2026 after killing his three children.

Rubio spoke exclusively to Channel 5 News. It's the first time he has talked on camera.

Rubio is currently being held at the Allan B. Polunsky Unit in Livingston, north of Houston. He’s been there since November 2003 and has spent nearly half his life — 23 years — on death row.

During that time, he's never spoken on camera. He agreed to sit down and speak with Channel 5 News.

"Since this all happened, I've always wanted to get my side of the story out there. Nobody ever wanted to listen to me, right?" Rubio said. "Everybody was seeing me as a monster that I'm not."

Rubio was convicted and sentenced for the murders that happened in March 2003. Investigators found his children, 3-year-old Julissa, 1-year-old John, and 2-month-old Mary Jane, dead.

Police said Rubio and his common-law wife, Angela Camacho, beheaded the children in their apartment.

"If you listened to the people that actually knew me, they would say that this is totally out of character for me. I was more of the protector of the family," Rubio said.

Investigators say Rubio and Camacho killed the children because they couldn't support them financially. Since his arrest in 2003, Rubio has claimed his children were possessed by demons.

Camacho originally backed those claims, according to investigators. In 2005, she pleaded guilty to three counts of capital murder to avoid the death penalty.

She's serving three life sentences. Rubio said his story hasn't changed since his arrest.

He was first sentenced to death in November 2003. His appeals have delayed his execution several times.

"If God can spare me this, that would be great. I don't want to bring sadness to my family members, those few that love me and care about me," Rubio said.

Earlier this year, the U.S. Supreme Court declined to hear his case.

You'll hear more of the exclusive interview with Rubio and the investigators involved in this case in the special report Echoes from Brownsville: The Rubio Murders. It airs on Thursday, May 21.

WATCH THE TRAILER FOR ECHOES FROM BROWNSVILLE: THE RUBIO MURDERS HERE

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