Brothers, 15 and 16, charged as adults in grisly stabbing death

It was an adult-sized crime, officials decided, so the Arroyo brothers deserved adult-sized charges.

Cristobal Arroyo, 15, and Luis Arroyo, 16, will face a murder trial together as adults after a judge in Tacoma, Wash., decided this week not to allow the younger brother to stand trial in juvenile court. The elder brother had already been charged as an adult.

Authorities say their crime is grisly, accusing them of killing 15-year-old Hector Hernandez-Valdez in their home and trying to hide the body from their sister and mother.

On June 1, 2012, Luis Arroyo tried to take Hernandez-Valdez’s money and marijuana when he came over to Arroyo’s home, authorities said. When Cristobal Arroyo saw his brother fighting, he stabbed Hernandez-Valdez, authorities said.

The Pierce County Prosecuting Attorney’s Office detailed what it said happened next, based on evidence and interviews with the Arroyo brothers.

“The brothers moved the victim into the bathtub to ‘drain him,’ ” the office said in a statement. “The victim was still alive and making noises. One of the brothers cut his throat to kill him. While [they were] attempting to clean the crime scene, their mother came home. She found reddish-brown stains on the floor, which they claimed was ‘chili.’ When she realized it was blood, the brothers claimed that a man had attacked them and they were forced to kill him. She went upstairs and saw a boy laying on a sheet, dead.

“Their mother drove to the neighborhood Tacoma Police Department substation to report the crime. Officers responded to the home and found the victim’s body, wrapped in a blanket, in a recycling bin in the alley behind the residence. During a search of the residence, investigators found two BB guns, a knife, a machete, a makeshift stabbing instrument, a baseball bat, and trash bags loaded with used cleaning materials. The weapons appeared to be bloodstained.”

Authorities said they discovered disturbing notes at the home and cellphone video of the brothers “swearing at and taunting” Hernandez-Valdez’s body.

Authorities said Hernandez-Valdez had been stabbed or cut more than 34 times in the head, neck, back, hands and chest; he also had a fractured skull and about 60 small puncture wounds on his back.

Cristobal Arroyo is scheduled to be arraigned Friday. Luis was charged as an adult in 2012.

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matt.pearce@latimes.com