Vampire left the party with a friend of Mario's, Lori Mejia, age 29.
About an hour later, he returned alone, with blood on his clothes.
"I killed her," he told Mario, and then left the scene.
Mario called the police. When the authorities arrived, he led them out behind the garage to a grisly scene.
"It was a horrific murder," Lieutenant Larry Kish of the Denton County, Texas, Sheriff's Office told CNN's "The Hunt with John Walsh." Mejia "was violently traumatized prior to her death ... and even after her death."
Who was "Vampire," why had Mejia left the party with him, and how did she meet such a violent end?
Putting the pieces together
Mario admitted to authorities that Mejia came to the party to make money as a prostitute. He had even negotiated her fee in advance, $100 per client.
Former Texas Ranger Tracee Murphree believes Mejia and Vampire left "with the intent of him paying her for sex and something went horribly wrong."
"Lori deserves the same justice as anybody else," Kish told "The Hunt," "as a homicide victim would deserve. We did not focus on her being a prostitute. We focused on finding this Hispanic male named Vampire, with no teeth, that had just brutally killed a lady."
No one at the party knew Vampire's real name, but Mario connected the authorities with a friend who did. "Vampire" was a man in his early 30s, Herbert (Herberto) Maldonado, who lived in the area with his 84-year-old girlfriend.
"To have an 84-year-old girlfriend was shocking in and of itself," said Murphree. "She talked to us about how Maldonado had beat her, and in the same breath she would tell us that she loved him."
"She didn't want anything to happen to him, but she did provide us with our next best piece of information, which was some photographs," said Murphree.
Armed with photos of Maldonado, investigators got a break: A girlfriend of someone at the party recognized the suspect. She didn't feel comfortable around him so wrote down the license plate number of his vehicle.
They entered the details in their system and got a match.
"We get a hit immediately that says this vehicle has been in contact with the Plano police, and they had actually arrested a Hispanic male for DWI," recalled Kish.
And that's where their luck ran out.
By the time they were on the phone with Plano police, the DWI suspect had bonded out.
"We get the identifiers on the person that was arrested and we quickly learn that is Maldonado, the same person that we're looking for," said Kish. "And we just missed him, like, within the hour."
According to Murphree, Maldonado's brother and other relatives were able to post bond. He was taken to Dallas, to be put on a bus to Mexico.
"We had him," said Kish. "He slipped through our fingers. He disappeared."
The hunt for Herbert Maldonado
"Twelve years later, it still bothers me, said Murphree, "having been that close and not been able to bring justice to this family."
Friends and family of Lori Mejia hope that the added exposure from CNN's "The Hunt" will at long last lead to Herbert Maldonado's arrest.
"People make mistakes, but what happened to her, that's just uncalled for," Mejia's friend and former roommate Elizabeth Burt told "The Hunt." "Nobody deserves to leave this world that way."
"I want to get this guy off the streets before he hurts someone else, and someone else has to deal with the pain we're living," said Burt.
Herbert Maldonado has a large mole on the left side of his face near his nose. His front teeth are missing and other teeth protrude. He has tattoos on both his left and right upper arm. He has worked on a sod farm in the past and might be working a similar job somewhere in the U.S.
If you've seen Herbert Maldonado or have any information as to his whereabouts please make the call. 1-866-THE-HUNT or go online to CNN.com/TheHunt. We'll pass your tip on to the proper authorities and if requested will not reveal your name.
See more of Maldonado's case on "The Hunt with John Walsh
," at 9 p.m. ET/PT Sunday, August 23.