'I had become a monster:' Convicted killer's inner thoughts from the grave

For nearly two decades, Texas investigators kept tabs on a man in connection with the brutal rape and murder of his ex-wife, Susan Woods, who was found dead in her bathtub.

The real killer, however, was revealed in 2006 through new forensic technology not available in 1987 and it was used to apprehend and convict Joseph Scott Hatley.

And even though Hatley was sentenced for his crime, investigators said there were still unanswered questions about what drove him to commit such a heinous act.

But after Hatley died following his release from prison, an investigator was able to get some answers to those questions when he was given the killer's dark, disturbing writings.

"My God, I had become a monster," Hatley wrote.

A "20/20" episode airing Jan. 19 at 9 p.m. ET and streaming on Hulu the next day will look at the case and Hatley's 260-page writings which will be revealed on television for the first time.

Susan Woods, who was 30 at the time of her death, was living in Stephenville, Texas, by herself as she was going through a divorce with her husband.

Before he left, Michael Woods left a vulgar tape recording and handwritten notes in the home that berated Susan Woods and accused her of for destroying their marriage.

Investigators identified Michael Woods as their top suspect when Susan Woods was found murdered inside her home in July 1987.

"At the end of the day, everybody in town thought that it was Michael. That's what all the family thought; that's what friends thought," Lt. Don Miller, of the Stephenville, Texas, police, who took over the case in 2006 and eventually solved it, told "20/20."

Michael Woods repeatedly denied he was involved with Susan's rape and murder, contending he was in Indianapolis at the time. Fingerprints found at the scene never matched his prints.

Michael Woods would continue to live with the shadow of the investigation surrounding him and was depressed about the situation."If I had known something was going to happen to her, I would've never left," Michael Woods told "20/20."

"After I left, I kind of felt like she got murdered because I wasn't there to take care of her," he added.

Michael Woods spoke to a friend in 2005 about living in a constant state of fear over the suspicion by his former wife's family and investigators. The friend emailed the Stephenville police to inquire about the case. Miller took up the investigation and, six months later, looked to pursue new leads.

One of the things he looked at was DNA evidence found on discarded cigarette butts left at the crime scene that could not be analyzed with the forensic technology available at the time.

Michael Woods ultimately agreed to a DNA sample, which showed he was not a match to the samples found at the scene of the crime. Authorities cleared him of Susan Woods’ rape and murder.

Miller went back to the fingerprint evidence and sent it to the state's Automatic Fingerprint Identification System and this time it came up with a match: Hatley, who was in the system due to a 1988 arrest in Las Vegas for armed robbery.

When Miller looked more deeply into Hatley's criminal file, he found that a year after Susan Woods' murder, 16-year-old Shannon Myers filed a report with the police alleging that Hatley, who was 20 at the time, sexually and physically assaulted her [

Myers had filed a police report against Hatley for another assault less than a year later but he was never charged.

Myers told "20/20" that she told investigators that during the second assault, Hatley allegedly told her he had killed before.

A grand jury did not indict Hatley on the allegations from the second assault.

Miller said that the details of the alleged assault stood out to him, including the fact that Hatley was a heavy smoker.

"My mind is going back to Susan Woods' crime scene because everything is matching now, up to and including the cigarette butts," he said.

Investigators also learned that Hatley was an acquaintance of Susan Woods and that he actually attended her funeral.

On June 6, 2006, Miller and his partner brought Hatley in for questioning. He admitted that he had visited Susan Woods' home prior to her death, but didn't kill her. Hatley alleged that they got drunk and high and "fooled around," but denied having sex with her.

While Hatley was being interviewed, investigators were speaking to Hatley's wife, who alleged to police that he repeatedly physically abused her.

After Hatley consented to giving Miller his DNA, he went home, but the sexual assault allegations from his wife, prompted investigators to arrest him.

Hatley's DNA matched the samples found at the Susan Woods crime scene.

Susan Woods' family, who had long suspected her ex-husband and even sued him over her death, and her friends said they were shocked.

"It was very, very hard to take, but the evidence was there," Cindy Hayes, Susan Woods' friend and Hatley’s cousin, told "20/20."

Michael Woods said he felt vindicated.

"When they arrested Hatley I felt like he's going to go to jail for what he's done now, and that Susan's going be able to rest a little easier in her grave," he said.

Hatley took a plea deal and was sentenced to 30 years in prison for Susan Woods' murder. He refused to say why he killed her, only claiming he was in a "drunken fog."

Hatley was released from prison in 2018 after serving 11 years of his sentence. Three years later, he died after allegedly battling cancer.

The convicted murderer still didn't divulge what drove him to violence, stumping his victims' families and investigators.

But shortly after Hatley died, Miller got a call from a friend at the police station who had gotten a call from someone who claimed they bought the trailer Hatley had died in.

The caller told investigators they found many disturbing things inside, including writings.

"He gave me all of this. Of course, I didn't have any idea what it was. I brought it back and started reading it," Miller said.

Bryan Burrough, the editor at large for "Texas Monthly," who first wrote about Hatley's writings for the magazine and discussed the story on the podcast "Stephenville," provided the writings to "20/20."

In his writings, Hatley claimed he had been the victim of physical abuse by his mother. He said he struggled to fit in at school, and he continued explaining through the pages of his writings how he had violent thoughts throughout his childhood.

Hatley wrote that he allegedly tried to kill his mother.

"I had found a new drug, fear," he wrote.

Hatley wrote about he thought Susan Woods was flirting with and came to her house one night. After they allegedly talked, Hatley claimed he "overstepped my bounds," and Susan Woods slapped him.

Hatley claimed that what happened next was a blur, but he "brutalized her" and used a pillow to suffocate her.

"She was alive. I could have stopped, but I didn't," he wrote.

Hatley had some thoughts about turning himself in but kept on going about his normal routine as investigators probed others.

"I wish with all my heart that I could tell you I've mourned for what I'd done, but that would be a lie," he wrote.

For the first time, Hatley opened up about his assault against Myers and the threats he made against her.

"I had become a walking demon," he said.

Miller said the revelations were crucial in Myers' journey of recovery from her assault.

"I'm no longer Scott's victim," Myers said. "I took that back from me."