Joe Fanciulli won't forget the first impression he made of Carl Taylor and Sherman Ramon McCrary.

Fox News Digital was reminded by a detective that they were "east Texas men with very little education." They lived by their wits. They were, I thought, dangerous men. They were robbers, and they did many other criminal acts."

Fanciulli said that the two men formed a bond and chemistry when they met. They tried to outdo one another with their criminal activities. They went from simple robberies and murder to, as they said, "Dead girls don’t talk."

Wondery's true-crime podcast, "Families Who Kill" features McCrary and his son in law. "The series focuses on how two petty thieves from Texas assembled their family and searched for criminal opportunities in America's West before being caught by law enforcement. The taped confessions of one of these convicted murderers are also featured.

This case was previously investigated in an episode of Investigation Discovery's true crime docuseries. It was titled "Evil Kin".

Executive producer Alan Wieder stated that it was "astonishing" to him that the story of murder and depravity hadn't been told in an exhaustive way. "It was exciting for me as a storyteller -- the idea to bring to light the disturbing and complex story of an antisocial American family. All the psychological elements, a pathologically dependent family working together as a murder machine, were also fascinating to me.

Fanciulli worked for 20 years in Colorado's Lakewood Police Department, where he was a specialist in economic crime. A 1970 check fraud case brought him to the McCrary clan, which he would pursue for 2 years until he finally found justice for Leeora Looney's murder.

Fanciulli said that they lived in motels, and made a living writing bad checks. "I was a new officer in the police force. At the time, we didn't have detectives. As a patrol officer you did everything. I was involved in the check case and tried to find the family.

"Unfortunately they were forced to leave. They were very good at this. But I obtained warrants and pursued them. Eight months later, the Leeora murders occurred. Because I suspected that the Leeora family might have been involved in other murders throughout the country, I became involved.

Looney, 20, was reported missing from the Lakewood donut shop where she worked on the evening of August 20, 1971. Court documents show that the purse of the waitress was open and her car was parked next to the shop. Witnesses reported that two men were seen in the shop shortly before Looney disappeared. Later, they were identified as McCrary & Taylor. Looney's nude corpse was discovered in a field three days later. She was raped, strangled and shot in her head.

Fanciulli stated, "These were depraved mind," It's so simple. They were of little use to life. This is something I have said before: These guys would kill a human being as a bug would. They wouldn't care much about a human life. They were just looking to satisfy their greed for stealing money and demeaning women.

According to reports, McCrary's wife Carolyn and Taylor’s spouse Ginger sat quietly while Looney was shot. Fanciulli denied that he believed this was true.

He said that he believed the women were still at a Lakewood motel. They knew exactly what was happening. They lived in fear, I believe. They lived in fear of the two men and wouldn't cross them. It's as simple as that.

Looney's murder was linked to a series of rape-murders where most victims were taken from donut shops, according to the investigator. Taylor's fingerprints were taken from a coffee cup in the donut shop where Sheri Lee Martin, an employee, vanished. Shortly before Looney kidnapped her, the 17-year old disappeared. Martin was found later in Nevada desert, where she had been shot. The Deseret Times reported.

Fanciulli stated that DNA technology was only 20 years away. "The sketches that were based on eyewitness descriptions were uncanny. However, it was the fingerprint identification that sealed the deal.

McCrary, Taylor were in Folsom Prison in California in 1972 when Colorado authorities indicted them for Looney's murder. McCrary admitted to Lakewood police that he had murdered three Texas women, but these statements were not admissible under Texas laws. Although McCrary never confessed, Utah officers believed that Martin was behind the murder.

Oxygen.com reported that McCrary and his relatives were suspects in at least 24 additional murders. These cases involved young women who were last seen alive in donut shops in Colorado and Texas, Florida, Kansas City, Utah, and Kansas City between 1970-1971.

Fanciulli stated that he was certain there were other victims.

He said, "If Carl knew that you had evidence that could place him there," It was like a game. But you had to prove it. He didn't just say "I did it."

A Colorado grand jury indicted McCrary, Taylor and other suspects in the murder of Looney in 1972. The New Yorker reported that Ginger cooperated with law enforcement and was sentenced to just a few years imprisonment. According to The New Yorker, McCrary was found guilty by a jury and Taylor pleaded guilty. Both were sentenced to life.

McCrary was serving time behind bars when he took his own life in 1988. McCrary, 62 years old, would have been eligible to receive parole in 1997.

Fanciulli said, "One always blames the other." Sherman would tell you that Carl was the main man, while Sherman was only along for the ride. Carl said the exact opposite. But I never heard any remorse. There was much bragging, sidestepping, and excuses. However, there was never an instance of "I'm sorry, but I don't understand what happened to me, I feel terrible for the families and victims."

Fanciulli said that although the murders were considered to be among the nation's most notorious serial killings, they have been overshadowed in other cases that generated more attention. The internet is lacking details about the murders. His book "Death Roads," on the case has been out of print since a while.

The New Yorker noted that victims' relatives, along with those connected to the killers have made connections in the comments section of a website for a podcast.

Fanciulli stated that "a lot of children, grandchildren, and extended relatives have come forward." "Some families even find each other."

Fanciulli hopes that the podcast will show listeners how the killings continue decades later.

Fanciulli stated that there are "terrible people like these out in the world." "Unfortunately, they will continue to be out there. We must continue doing what we can to bring these types of people to justice.