The murder of Texas mother Heather Simpson last year appeared at first to look tragically familiar: An estranged husband discovers his wife in the company of a former boyfriend and snaps, committing a spontaneous and deadly crime of passion.

But the grisly March 2013 murder that shook the tiny, East Texas town of Ben Wheeler was anything but impulsive and unplanned, according to the county sheriff.

And Simpson’s family disputes that the mother of four was ever unfaithful to her husband — and are fighting to defend her name, and demanding that justice be served.

At the heart of the case — and the family’s fight — is the narrative of the crime as told by the only surviving witness, Moses Clemente, a 49-year-old ranch hand who at one time was engaged to the victim, and who was with her the night of the murder.

The investigating officer in the case, Van Zandt County Sheriff Michael Lindsey Ray, told FoxNews.com that in the early hours of March 24, 2013, Heather Simpson’s husband, Larry Maples, parked his car a half-mile from a home occupied by Clemente. At the time, Heather Simpson was meeting secretly inside the home with Clemente, her long-time former boyfriend, days after she “tried to make a break from [Maples].”

“[Simpson] had made herself unavailable to Larry Maples and he was trying to find her,” Ray told FoxNews.com. “He was stalking her.”

Armed with a Colt .45 handgun, Maples quietly entered the house through an unlocked door and shot each of the occupants, first hitting Clemente in the abdomen, then firing four bullets into Simpson, the last being a fatal shot to the head, Ray said. Clemente survived his wound, and Ray said Simpson survived Maple’s first two shots — and could have survived the third — but died from the fourth and final shot to the head.

Maples called his family after the shootings, telling them what he’d done and indicated he was thinking about taking his own life, Ray said. Either Maples or his family then called 911. Police arrived at the house shortly thereafter, found Simpson’s body and the wounded Clemente, and took Maples into custody, Ray said. Maples later confessed to the crime, Ray and Van Zandt County District Attorney Chris Martin said.

Based on evidence collected by Ray and his investigators, Maples was charged with capital murder — meaning he could face the death penalty.

“This crime was pre-meditated,” Ray said. “He entered that home to commit a murder. To say this is a crime of passion is not accurate. He had more than ample time to turn around and stop what he was doing.

“He is a cold-blooded killer,” Ray said.

What Heather Simpson was doing at the house with Clemente when Maples entered and began shooting is at the heart of her family’s quest to clear her name. Further complicating the case is Clemente’s account, which Ray says has changed several times.

While Ray declined to comment on the relationship between Simpson and Clemente at the time of the murder, family members said the 34-year-old mother — desperate to escape what they called an abusive marriage — was confiding in Clemente as a friend.

“We were just sitting there talking,” Clemente told FoxNews.com. “She just needed someone to talk to and she came to me as a friend. He [Maples] was enraged because she wanted a divorce.

“He made her suffer,” Clemente said.

There were troubling signs from the beginning in Simpson’s relationship with Maples, her family said.

Heather Simpson lived for 10 years in Ben Wheeler, a small town of about 400 an hour east of Dallas, and worked at the local post office, where she was known for greeting senior citizens with a hug. Her family admitted they were unsure about the details leading up to a secret marriage to Maples, her second husband, in November 2012. Her older sister, Lori Simpson, said she learned of the marriage a few months later.

“I really raised my sister,” Lori Simpson said, saying her sister’s secret marriage was “highly unusual.”

By January 2013, Maples made Simpson put all her money into one account and, “said she couldn’t spend any of it,” Lori Simpson claims. “He started becoming controlling of her every move.

“Heather was scared,” her sister said.

A month later, in February 2013, Lori Simpson claims her sister found out that the 44-year-old Maples was being investigated in a 2008 child molestation case, which led Heather Simpson to tell Maples she wanted a divorce — a claim that Sheriff Ray could not completely confirm.

No formal separation or divorce papers were ever filed, Lori Simpson said.

“She was starting to learn his secrets,” Lori Simpson claims.  

What happened next stunned Lori Simpson and her family.

Maples was ordered released from jail on June 27, 2013, because Ray’s department failed to produce a report on the crime within 90 days, as required by Texas law.

District Attorney Chris Martin told FoxNews.com that it was “atypical for a law enforcement agency to not produce an initial report within a 90-day period.”

Ray defended his department’s actions, saying he was waiting for critical information — including autopsy reports and forensic evidence — from the Texas Rangers that made it difficult to produce a report within the required timeframe.

“It is hard in this town to get a capital murder case ready in 90 days,” Ray said. “We don’t have the resources of large metropolitan police departments. It’s incumbent on us to ask for help and to receive help from other agencies.

“We’re actually still waiting on biological evidence,” he said, adding that such information has not yet been sent from the lab to the Rangers, the primary forensic investigation division within the Texas Department of Public Safety.     

Maples was re-arrested last Sept. 26, but this time on charges he sexually assaulted a child under 14, District Attorney Chris Martin said. Maples remains behind bars at the Van Zandt County Jail pending trials in both cases.

“After receiving and reviewing the evidence presented regarding Larry Michael Maples and the murder of his wife, Heather Maples, it is apparent that Mr. Maples committed the offense of capital murder,” Martin said in a statement Monday. “We intend to prosecute him aggressively, keeping in mind the full range of punishment, which includes seeking the death penalty or life imprisonment without parole. We are driven to seek and receive justice for Heather Maples.”

Martin said his office filed papers to seek the death penalty in the Simpson case, but that no formal decision has been made yet “in consideration of the family’s wishes.” He said the family indicated they wanted life in prison without the possibility of parole.

“It’s ultimately my decision, but of course I like to take my victims’ view into consideration,” Martin told FoxNews.com. “It’s important to me that their feelings be considered.”

Lori Simpson, however, recalls a different conversation with prosecutors.

She told FoxNews.com that they said, “We can’t afford to seek the death penalty,” and that, “It would cost more than $1 million to do it because he [Maples] would seek appeals.

“It would go on for years and years,'” Simpson claims she was told. When the family heard that, Simpson said they opted for life in prison without the possibility of parole — though nothing has officially been decided.

For the Simpsons, claims of infidelity churning around the small community — and the frustrating procedural twists and turns of the legal system — have only compounded their tragedy.

“She loved everybody, and everybody loved her,” Lori Simpson said of Heather, who loved karaoke and would often sing to her father his favorite song — the Beatles’ “Yesterday.”

Lori Simpson said her terminally ill father’s last wish is to see justice done for his daughter — and her reputation cleared.

“She lived in the moment and didn’t take life too seriously,” Simpson said. “She truly had a heart of gold.”