The man accused of shooting and killing a female Navy Corpsman last Friday outside of her Oceanside apartment was a former Marine who deserted and was discharged after being diagnosed with Schizophrenia.

Eduardo Arriola, 25, held a blank stare throughout his arraignment Tuesday while family members of the victim, 24-year-old Devon Rideout, met details of the alleged crime with sobs and tears.

Prosecutors say Arriola “ambushed” Rideout in broad daylight as she exited her apartment to take her dog for a walk. They say she had just gotten home and was still wearing her Navy uniform when she was killed.

Police officers were called to the complex on Los Arbolitos Boulevard just before 4 p.m. and arrived to find Rideout in the breezeway outside her unit. She was suffering from gunshot wounds, police said.

First responders tried to revive her but she was pronounced dead at the scene. Prosecutors said Arriola tried to prevent witnesses from getting to Rideout to help give her emergency aid.

Arriola, who lived in the unit above Rideout, was arrested the next day on suspicion of murder.

Prosecutors said Arriola deserted the Marine Corps in 2016 and fled to Mexico. When he returned to the states he was diagnosed with schizophrenia and discharged in 2017.

Investigators say Arriola fired five shots from a gun he purchased legally from an Oceanside gun store in May.

Deputy District Attorney Keith Watanabe said he believed Arriola purchased the .38 Smith and Wesson handgun from Ironsides shooting range.

The gun store apparently didn’t have access to his military records and didn’t know of his mental illness.

Investigators say Arriola and Rideout did not know each other, but they did find Rideout’s name and two others along with the letters “RIP” written on the radiator of Arriola’s car. Investigators are still investigating the other two names.

“This was a heinous shooting committed in broad daylight in front of witnesses,” Deputy District Attorney Keith Watanabe said. “The defendant had to have been lying in wait because the victim only made it a few steps out her front door when she was gunned down.”

Arriola could face the death penalty if convicted.