Updated

A man accused of killing two girls along a rural Oklahoma road in 2008, but who wasn't arrested until after being questioned in his fiancée's death three years later, pleaded guilty in both cases Thursday.

Kevin Sweat, 28, entered guilty pleas to three counts of first-degree murder in Okfuskee County District Court. Prosecutors dropped plans to seek the death penalty after Sweat agreed to waive his right to a jury trial. His bench trial, before only a judge, was scheduled to begin Monday.

The girls — 11-year-old Skyla Whitaker and 13-year-old Taylor Paschal-Placker — were fatally shot as they walked down a road near Weleetka in rural eastern Oklahoma. Sweat was not suspected in their deaths until police questioned him in the 2011 slaying of his fiancee, Ashley Taylor.

Investigators said Sweat confessed during a videotaped interview with state investigators, telling them he shot the two girls because he thought they were "monsters" coming at him.

Sweat's attorneys had argued that Sweat was not mentally competent when he waived his Miranda rights before participating in the interview, but a judge agreed this year to allow prosecutors to use the video as evidence. The video had been played at previous hearings.

In the video, Sweat first tells Oklahoma State Bureau of Investigation agent Kurt Titsworth he had nothing to do with the girls' deaths, saying "there would be no point to shooting kids."

But Sweat eventually said he shot what he said were "the demons" who approached him along a rural road where the girls' bullet-riddled bodies were found.

"I see demons, vampires ... monsters, demons, whatever. I do have some problems," Sweat said. "I was scared. ... They were still coming at me, so I shot them."

Taylor, his fiancee, went missing in July 2011 after telling her parents she was eloping with Sweat.

The three murder cases were combined after prosecutors suggested a connection while questioning Sweat's mother and her cousin during a pre-trial hearing about statements Sweat made about his relationship with Taylor and his desire to break up with her.

Prosecutors asked if Sweat had told them Taylor would spread lies about him if he broke off the relationship, including blaming him for the girls' deaths. However, at the time, Sweat's mother and cousin said they didn't remember Sweat saying Taylor had threatened to tell authorities he shot the two girls.