Eduardo Arriola “must have lied” on paperwork.

A former Marine killed his neighbor after she came home from work and took her dog out for a walk, a San Diego County prosecutor alleged in court July 24, 2018.

Eduardo Arriola, 25, made his first appearance in court on Tuesday. Sheriff’s records describe Arriola as 5 feet 7 inches tall and 200 pounds. He is held without bail.

Arriola pleaded not guilty to first-degree murder with the special circumstance of lying in wait, which could mean life in prison without parole, or the death penalty, if he is ultimately found guilty.

Prosecutor Keith Watanabe said 24-year-old Devon Christian Rideout came home “after a hard day’s work” on July 20, 2018, and quickly took her new puppy out of her apartment for a walk. “She only made it a few steps outside of her door,” the prosecutor said.

Rideout was a Navy Corpsman who worked on nearby Camp Pendleton, and was still in her military uniform when she was confronted by a man who lived upstairs, the prosecutor alleged.

Arriola emptied his five-shot Smith&Wesson revolver into his victim, according to Sheriff’s detective Brent Keys. The detective said the victim suffered three shots to her torso and two to her head. Rideout was declared deceased on the scene.

According to the prosecutor, Arriola told first responders, “I used lethal force because she was trespassing.”

The deadly assault happened “in broad daylight” on a Friday afternoon after 3 p.m., in front of multiple witnesses, according to prosecutor Watanabe. Bystanders who moved to help the gasping woman were prevented by the shooter, the prosecutor said.

Rideout was “truly an innocent victim,” the prosecutor said. She had worked as a Navy Corpsman for five years and was going to school to become an occupational therapist.

Arriola lived in the apartment directly above the victim, with his mother and brother and sister, at 550 Los Arbolitos Boulevard, in Oceanside. The alleged shooter had no known relationship with the woman he shot, the prosecutor said.

Arriola was a Marine in 2016, but he deserted and went to Mexico; he returned to the United States in 2017 and “turned himself in”; he was diagnosed as schizophrenic and discharged from the Marines that same year, according to the prosecutor.

Oceanside police looked under the hood of Arriola’s new car, a 2018 Toyota Corolla iM, and saw that someone had used a black Sharpie marker to write on a tank connected to the radiator. Police found the name of the deceased woman plus the names of two other persons written there, along with the words REST IN PEACE, the prosecutor said.

“QURAN” and references to Quran verses were also written in the engine compartment, the prosecutor said.

Investigators found a Quran and a handwritten journal on the suspect’s “bedside”, the prosecutor said.

Two months prior to the shooting Eduardo Arriola purchased a revolver from Iron Sights, a retailer in Oceanside, the prosecutor said. That retailer does not have access to any military database and therefore would not be aware of Arriola’s "schizophrenic” diagnosis, Watanabe said, and he speculated that Arriola “must have lied” on paperwork which would have asked if he had a mental illness.

Defense attorney Lindsay Itzhaki stated that Arriola was born and raised in Oceanside and has no criminal record, and she requested the judge to set “reasonable bail.” Watanabe argued that the defendant “is a danger to the community.” Honorable judge Robert Dahlquist ordered Arriola to remain in custody without bail, and set a bail hearing date of August 14.