GAINESVILLE, Fla. -

On the 25th anniversary of the disappearance of Tiffany Sessions, Alachua County Sheriff Sadie Darnell says it's "highly, highly probable" that Paul Rowles -- a man who died in prison one year ago doing time for murder, kidnapping and sexual battery -- was responsible for the disappearance of the 20-year-old college student in 1989.

"Come forward if you were involved," Darnell said in a Thursday morning news conference.

"We need the public's help. We are looking for a very small needle in a very big haystack," said Hilary Sessions, Tiffany's mother. "We just need one tip."

The Sheriff's Office invited the media to the site where authorities are digging for new evidence, where they released details of the investigation, case photographs and information regarding the suspect in hopes that disclosing it will result in leads from the public that may help solve the case.

Session's father, Patrick Sessions, a prominent South Florida real estate developer, used his connections with former Miami Dolphins quarterback Dan Marino and other NFL players to gain attention to the case, but his daughter was never found.

Paul Rowles Rowles (shown in Florida Department of Corrections photo) was 64 when he died in February 2013 while in state custody. According to Patrick Sessions, Rowles was in Gainesville working as a pizza delivery man and for a construction company in the city at the same time Tiffany Sessions and another woman whose body was recently discovered lived there.

"He was a stalker. He planned all of his crimes in meticulous detail. He was very detail-oriented, (had obsessive-compulsive disorder)," lead investigator Kevin Allen said. "I'm sure he met her either from a pizza delivery or when he was putting up construction scaffolding at the apartment complex on the walk that she took every day. I'm sure he planned this crime out well in advance. He probably practiced it several times, and when he took Tiffany, he took her to her grave."

The site where investigators are searching is where the body of Beth Foster was found in 1992. It wasn't until 2012 when DNA evidence pinpointed her killer as Rowles.

After Rowles died last year, investigators went through the stuff in his prison cell. They found the date Sessions vanished written in his calendar -- written "#2 2-9-89 #2" -- and they believe the "#2" stands for his second victim.

His first was a woman from Miami whom he was convicted of killing in 1972 but was released nine years later.

"Beth Foster was found in the wooded area behind me," Darnell said. "Her grave is marked with an orange stick in the dirt. We believe this was potentially a dump site also or disposal site for Tiffany. We have dug up this area. We had a major dig a little over a week and a half ago. We're back to finish the effort, hoping to find the remains."

At Thursday's news conference, investigators displayed photo boards of Rowles at various ages, the red Bronco he drove at the time and a timeline of his life, hoping it will trigger someone's memory.

"I know it can be closed," Hilary Sessions said. "We just need that little piece of information that somebody has, and I want to make sure you're not going to get prosecuted or go to trial because Paul Rowles is dead and there's no possibility of a trial."

"This is proof that there are evil men among peaceful people," Gainesville Mayor Ed Braddy said.

Patrick Sessions is hoping that if his daughter's remains are recovered, DNA will point toward a killer, or that Thursday's announcement will jog someone's memory about Tiffany's disappearance.

Jason Sessions, Tiffany's younger brother, said coming back to Gainesville and watching police search for evidence in how she disappeared hasn't been easy.

"This has been tough. Standing here for two weeks watching them excavate this site looking for Tiffany's remains has been a difficult process for us," said Jason Sessions. "It's been very painstaking, it's been long, it's been a difficult process for me for sure. It stirred up a lot of emotions that haven't been that strong within our family in a number of years."

The Alachua County sheriff says it's "highly, highly probable" that Rowles killed Tiffany. Jason Sessions thinks of Rowles the same way he would any other convicted killer.

"Yeah you know, I don't, as I was saying before, I don't necessarily think of this guy any differently than I do the other criminals that we've been investigating. There's a lot of nasty people out there," said Jason Sessions. "There's a lot of people everywhere that do harm to people, especially women. It's a terrifying world out there and you can't live every day in fear, but you have to be cognizant of what's around you."

The lead investigator for the case went to Miami to try to speak with Rowles before he died but it was too late. Rowles was in ICU on a ventilator, dying from lung cancer. He'd been asked about Tiffany Sessions once before after DNA linked him to Foster's murder but he refused to cooperate.

The Sheriff's Office set up a special number for tips in the Session case: 352-955-1818.

Jacksonville connection to Sessions case

Many wonder how Rowles could have gotten out of prison after nine years when he was sentenced to life.

The Florida Parole Commission in 1985 ruled to release Rowles from a life sentence for murder after he served only nine years in prison. He was to undergo psychiatric counseling and register as a sex offender.

That apparently didn't happen until after his Duval County convictions in 1994, and after he is believed to have kidnapped and murdered Sessions. The commission's decision contained this note: "There is a reasonable probability that while on parole the inmate will live and conduct himself as a respectable and law-abiding person ... compatible with ... the welfare of society."

"I'm not sure," Allen said. "He was sentenced to life in prison without the possibility of parole and he was released in 1985. Now, he did marry a prison employee and maybe she helped him get out. I don't know."

That's what many are asking now, but Rowles was never questioned about Sessions' disappearance or Foster's murder.

All three crimes had Gainesville connections. Rowles took his last victim to Jacksonville.

"The last victim actually survived," Allen said. "Paul Rowles drove all the way from Jacksonville to Clearwater and kidnapped one of his neighbors -- a 14-year-old minor -- drove her with duct tape on her eyes and duct tape around her hands. A wooded area we believe is behind us. He said this is where people left things they did not want to be found. Then drove her to Jacksonville and committed sexual battery against her."

Channel 4 crime analyst Ken Jefferson worked for the Jacksonville Sheriff's Office in sex crimes at the time. He remembers this case but does not know why connections to other crimes were not made.

"In hindsight, we did not have all the technology like we have today, and we did not have all the direct connections back then that we have today," Jefferson said. "But I do think what could have been done more differently is communicate with the other agency."

Rowles lived in Arlington in the 1990s. It wasn't far from the Jacksonville University campus that he committed that last crime that landed him in jail.