Authorities have named the victim as 28-year-old Jose Ramirez , from California.
They believe he was killed around five years ago.
Clay County Sheriff Kenny Lemons says Ramirez had served in the Army and had been stationed at Fort Sill -- which is where Lemons says he met his accused killer.
Ramirez's family filed a "missing person's report" in December of '07 ... and is just now getting some answers.
Jose Ramirez's body ... dumped in a shallow grave near a trash pit ... left there for about five years.
After Friday's positive I.D. ... authorities in California broke the news to Ramirez's mother.
Clay County Sheriff
"It's not information that any mother or father wants. I can't imagine -- having children myself -- having that information given to me, but like anything else, you certainly need closure, & this is the first way of -- first step in doing that."
Thirty-year-old Justin Green is charged with the murder.
Witness statements say Green shot Ramirez with a rifle ... then called his mother, Terri Green, to help clean up and hide the body.
Terri allegedly called her daughter, Brittany, to help.
Brittany's friend, Stephanie Heaston Corral, is also charged in the coverup.
"Twenty-two years of doing this, this is the first time I've ever been involved in an investigation that was this bizarre. It certainly is one that's out there. It doesn't come across very often. And especially the fact that you have such an old homicide that's solved so quickly. It moved really fast & I had some real good guys on it, & we just worked together with the ranger service -- without the rangers, I don't think we could have made near that progress."
Officials said Brittany Green told them her brother shot Ramirez because Ramirez didn't believe in God ... and that Ramirez was also reaching for a gun.
"We can't really verify a lot of that - that was just information that was given to us by other people. So - but the case is still actively moving forward, & we're trying to come to the motive.
"We feel like we live in a real safe community in a real safe county. And those kinds of things don't happen in Petrolia, Texas. It's - it's shocking & surprising."
Justin Green and his mother were arrested in Phoenix, Arizona ...
His mother had originally refused to waive extradition ... authorities just brought her back early yesterday morning. All three Greens remain jailed ... Corral has posted bail.
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