GAINESVILLE (CBSMiami) – After 25 years detectives investigating the disappearance of Tiffany Sessions, a University of Florida student who vanished while out for a walk, now have a promising lead.

Alachua County Sheriff’s Office Detective Kevin Allen has named serial killer Paul Rowles as the primary suspect in the case, according to CBS News. Allen has been working on the case for the past year during which a timeline was established, and other evidence collected, that pointed to Rowles.

The Alachua County Sheriff’s Office will officially confirm that Rowles is their prime suspect at a news conference on Thursday.

Sessions, 20, was reported missing on February 9, 1989 after she didn’t return home from a routine power walk on Williston Road in Gainesville. At the time, Rowles worked as a pizza delivery man and for a construction related company near Session’s path.

Tiffany’s parents Pat and Hilary, who live in South Florida, rushed to Gainesville to look for her.

“We all were trying to get a handle on what possible explanation. Did she have a boyfriend nobody knew about? She didn’t have her wallet, her driver’s license. Her car was there. And that was the scary part,” Pat Sessions told CBS News.

A massive search was launched, but no trace of her was found.

Jim Eckert, one of the lead detectives in 1989 said, “This woman literally vanished off the face of the Earth.”

According to investigators, Rowles murderous past began in 1972 when he killed Linda Frida in Miami. Rowles confessed to the murder and was sentenced to life in prison in 1976.

In 1985, he was paroled and moved to Pinellas County. Three years later he moved to Gainesville.

Three years after Sessions was reported missing, another Gainesville woman Elizabeth Foster was reported missing. Her body was found in a wooded area off Williston Road about a mile from where Sessions went missing.

In 1992, Rowles moved to Jacksonville.

In January, 1994 Rowles kidnapped and sexually assaulted a teenage girl from Clearwater. On the way back to Jacksonville, investigators said he stopped in a wooded section of Gainesville and told the teen “this is the kind of place people dump things they don’t want to be found again.”

Rowles was arrested and confessed to the kidnapping and sexual assault. He was sentenced to 19 years in prison.

In February, 2012 investigators matched DNA at the Foster crime scene to Rowles.

In January, 2013 Rowles was interviewed about Sessions’ disappearance. The following month, Rowles died in prison of natural causes.

That’s when police made a startling discovery.

Investigators said Rowles kept an address book with information on his victims. In the book, Frida was listed as Rowles’ first victim. Investigators say there is a possible reference to Foster in the book. But the most shocking find was a simple notation “#2 2/9/89 #2”. Investigators noted that it was the date Sessions went missing and the #2 possibly stood for his second victim.

Police are now excavating the site where Foster’s body was found, hoping to find Sessions.

“You remember this guy isn’t around to fill-in the blanks. You can only imagine—and I can tell you that imaging–is not always the best thing because so many different thoughts run through your mind—did my daughter suffer?” said Gary Karp, a family friend.

Ted Scouten