"The gun just went off," Greer said. The next day, police let Greer walk free and he's been running from the law ever since.
It all began several years earlier, after Esquivel's husband hurt his back in a work accident. When that happened, it was up to her to find a way to support her husband and their three kids.
She was flattered when she was offered a relatively high-paying job as an exotic dancer. Her husband and her mother tried to talk her out of it, but the money was good, so she took the job.
Esquivel soon made friends with a tough guy named William Greer. It wasn't long before she and her husband were separated, and Esquivel had moved in with Greer.
Then, her mother said, the violence started. Esquivel told her mother that Greer would hit her sometimes when he got upset.
It all came to a head in December 2006, when police in Liberty County, Texas, were called to the scene of a pickup truck parked in a ditch.
The engine was still running.
Searching the pickup, they found Esquivel's pink cell phone. Suddenly Greer -- wearing nothing but a shirt in cold weather -- approached the truck -- telling police it was his vehicle.
That's when Greer started rambling — going on and on about how much he loved Esquivel, her death and a gun that "just went off."
"We had a confession obviously," Sgt. Paul Lasco Liberty County Sheriff's Office told CNN's "The Hunt with John Walsh." "But without some sort of evidence, mainly a body, DNA, crime scene, something, there's nothing you can do."
Police booked Greer for public intoxication. He made bail and then immediately fled the state.
Later Greer's young sons came forward and told authorities that they had overheard Greer and Esquivel arguing, followed by gunfire. In March 2007, Harris County, Texas, authorities indicted Greer for murder in the killing of Tammy Esquivel.
During the past ten years Greer has allegedly been spotted in Louisiana and in Kentucky, where he struck up a romance with another woman -- Kelly Richardson.
William Joseph Greer
Height: 5 feet, 10 inches
Weight: 180 pounds
Distinguishing features: Missing toe on right foot; may be armed and dangerous
Alleged sightings: Kentucky, Louisiana
Tammy Marie Esquivel
Kelly Richardson, Dayton, Kentucky
"He was a real charmer. ... He was a real ladies man. ... He would get nervous if I started speeding or ran through a yellow light. ... You can only put on an act for so long and I knew something just wasn't right. ... It probably wasn't even a month after that that he just disappeared."
"He stole some money I had been saving to buy a new couch. He stole some of my jewelry."
"It hurts me inside to know that I was with someone that killed that woman and left those children like that. It's sad."
Harris County, Texas, Sheriff's Office
Sgt. Craig Clopton
"I had our dive team come out. We didn't find anything in the water. We didn't find anything in the whole area we searched. To this date we've never found Tammy's body."
The victim's mother
Tammy's mother, Marcia Esquivel, wears her daughter's name tattooed on her chest, close to her heart. "I want to catch Greer and I don't plan on stopping looking for him." "Tammy and Ron, when they first got together, were like wine and strawberries," Marcia Esquivel said. "They were beautiful together. She was a stay-at-home mother. Every day he got up and went to work and provided for his family. They never wanted for nothing."
Harris County, Texas, Assistant District Attorney
"I don't think that Tammy can rest in peace or her family can properly mourn her until we have him in custody and until he accounts for his deeds," said Harris County, Texas, assistant district attorney, Katherine McDaniel. "And it's only by putting him in custody that we can take him to trial and have him take responsibility for what he's done."