FORT WORTH, Texas -- From behind a glass window at the Tarrant County Corrections Center, 18-year-old Mariano Sanchez told WFAA he had no part in the murder of a young couple, who were found buried in a shallow grave in an Arlington backyard on Tuesday.

"I just want to know why am I in here for something I didn’t do," he tells us.

Police believe otherwise.

"I don’t feel bad right now. Why? Because I have nothing to do with this," Sanchez says.

One of the victims, identified Friday as 27-year-old Erick Zelaya, was shot to death and decapitated. Police say his head had been found days before his body was discovered, on an Arlington walking path with a sign written in Spanish next to it: "La Raza Se Restreta y Faltan 4."

His body was discovered in a shallow grave behind a house, along with the body of his 17-year-old girlfriend Iris Chirinos. Both had been shot multiple times.

Sanchez claims he knew nothing about the decapitation until police told him about it, and he believes the message next to the head was a threat directed at him.

"They're going after four more. That’s what I'm telling you," Sanchez says.

But Arlington police believe both Sanchez and another man, 28-year-old Hector Acosta-Ojeda, known as "Cholo," cut Zelaya's head off.

Hector Acosta-Ojeda (mugshot from previous crime)
Hector Acosta-Ojeda (mugshot from previous crime)

Acosta is in the Arlington jail, which doesn't allow interviews.

"Did you take part in either of the killings?" we ask Sanchez.

"No ma'am," he responds.

"Another witness [in the affidavit] said you cut off the victim’s arms, is that true?"

"No ma’am," he answered again, saying he had nothing to do with the crimes at all.

He does say he feels safer in jail than out.

Sanchez is also being held on a burglary of a habitation warrant and a possession of a controlled substance charge.