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VISTA (CNS) – A man was convicted of first-degree murder Thursday for gunning down a female Navy corpsman at an Oceanside apartment complex nearly four years ago.

Following a day of deliberations, a Vista jury also convicted 29-year- old Eduardo Arriola of a gun-use allegation, plus a special circumstance allegation of lying in wait, meaning he will face life imprisonment without the possibility of parole when he is sentenced for the July 20, 2018, killing of 24- year-old Devon Rideout.

Both Arriola and Rideout were residents of an apartment building at 550 Los Arbolitos Blvd., where prosecutors allege Arriola shot Rideout multiple times at around 4 p.m. She died at the scene, according to Oceanside police.

Prosecutors say Rideout, Arriola’s downstairs neighbor and a Navy hospital corpsman stationed at Camp Pendleton, was walking her dog when Arriola shot her. After the shooting, he repeatedly claimed to bystanders that she was a trespasser.

Investigators searched the defendant’s car and found the victim’s last name scrawled in black permanent ink on the car’s radiator tank. A list of other names and words were also written on the tank, with the final entry “R.I.P.” concluding the list.

Arriola was a former Marine who was discharged for desertion and later diagnosed with schizophrenia, leading to four hearings between the killing and his trial to determine whether he was mentally competent to stand trial. Three separate doctors found him competent, according to court documents.

The schizophrenia diagnosis and his discharge from the military also should have precluded him from legally purchasing the firearm used to kill Rideout, according to a lawsuit filed earlier this year by Rideout’s mother. The suit alleges Arriola should have been entered into the criminal background check system used by firearms sellers and that various government entities failed to report to the proper authorities that he was a prohibited person.

The murder weapon was purchased from an Oceanside firing range about two months prior to the killing.

Arriola’s sentencing hearing is scheduled for June 17.