Peter Reiss won't call serial killer Joel Rifkin a friend, but they have definitely forged a relationship over the years.

That has led to the forthcoming A&E special "Cold Case Files: The Rifkin Murders" in which authorities attempt to learn the names of two of Rifkin's unidentified victims.

Rifkin was a landscaper who is believed to have murdered 17 women in New York during the 1990s. He is currently serving more than 200 years in prison after he was convicted in 1994 for the murder of nine of the women.

Reiss, who is one of the producers of the special, told CNN he first met Rifkin1998. Reiss had contacted him for a science documentary he was working on about how biology may factor into killing.

"I was intrigued by Rifkin because he didn't seem to have a lot of the normal traits that people associate with being a serial killer," Reiss said. "He came from a loving home with loving parents, had a good relationship with his sister, went to good schools and kind of was given a lot of the things that you need to succeed in life. And, yet, he still turned into a serial killer."

Rifkin was interested in participating in the documentary and the two began talking, Reiss said. Years of conversations between the two men followed.

"He is very disarming. He comes across as normal when you sit there and talk to him," Reiss said of Rifkin. "He asks you questions about what's going on in your life and tells you things on in going on in his life. And so you have to remind yourself that you're talking to a serial killer and that you're there for a reason, which is to get information."

The ease of their relationship helped Reiss build a rapport with the New York investigators working to identify two of Rifkin's victims known simply as "victim number six" and "victim number nine."

Rifkin was an active participant in the cold case special, Reiss said.

"He was very forthcoming. He said that he wanted to help these families get closure and he provided a lot of information that checked out," Reiss said. "He was helpful in trying to get these identities made. But what his ultimate motive is I'm still unsure about."

For Reiss, he is motivated to do right by the women who were killed and their families.

"It's an honor and privilege to get to tell their stories. A lot of the world has forgotten about these women, but [their families] never have," he said. "And they're still searching for answers. What I've learned is that closure is real, and that if you don't have the answers of what happened to your loved one, it's going to eat at you and cause you pain throughout your life."

The two-part special premieres Saturday, Sept. 30 beginning at 8 p.m. ET on A& E.