Her words proved to be an ominous forewarning, now that University of Virginia sophomore Hannah Graham, 18, has been missing since Sept. 13 – one of a number of young women who have disappeared in central Virginia since 2009.
"For the past five years I have been saying, 'There's a predator out there. A serial predator. Everybody be careful. Look out for one another. Participate in your community. Know your neighbors,' " says Harrington, 57, who, with her husband, Dan Harrington, founded Help Save the Next Girl, a nationwide non-profit aimed at trying to prevent crimes against young women by promoting personal safety.
"I have been saying this is a local predator who is hiding in plain sight in your town," she says. "This is not a drifter. This is somebody who is eating at McDonald's and putting gas in his car. He is here among you. He doesn't look like a monster and that’s why he's blending in."
Jesse Leroy Matthew Jr., who police believe is the last person to be seen with Graham, was arrested on Sept. 24 in Galveston, Texas, and charged with abduction with intent to defile in connection with her disappearance.
Virginia State Police sent the investigation in a whole different direction when it announced five days later that investigators have found new forensic evidence linking Matthew to Harrington's murdered daughter. Her unsolved murder had already been linked by DNA to the rape of a 26-year-old woman in Fairfax, Virginia, in September 2005.
With police calling the evidence a "significant break" in the case, Harrington says she is hopeful that some light may be shed on what exactly happened to her daughter, a Virginia Tech student who was last seen on Oct. 17, 2002, after attending a Metallica concert on the UVA campus.
"I was told early on that most likely we would find Morgan's murderer from another victim," says Harrington, whose daughter's remains were found three months after she disappeared in a remote field in Albemarle County.
Like her daughter, Graham was wandering alone in Charlottesville – at night – when she vanished.
When the Virginia State Police called Harrington telling her that they had found a forensic link between Matthew and her daughter, "Your heart squeezes," she says, "but it's not a celebration because the cost of it is another young woman who is missing."
Her main focus right now is continuing to work to prevent other young women from harm – and finding Graham.
Immediately after Graham disappeared, Harrington and her husband drove to Charlottesville, where they put up a "Please Find Hannah" sign on the Copeley Bridge, where her daughter was last seen. They also posted flyers and urged anyone with information about Hannah's disappearance to come forward.
On Sept. 30, during an appearance on NBC's Today show, she urged Matthew to divulge any information he may have about Graham.
"I would like to appeal to him to please give the family information where Hannah is. We need to find Hannah," she said.
Waiting for More EvidenceAs authorities continue to search for Graham with drones, ATVs and canine units, Matthew is being held without bond in the Albemarle Charlottesville Regional Jail.
As he awaits his first court appearance in connection with Graham's disappearance on Dec. 4, police are reopening cold cases to see if there is a link between him and other women who have disappeared in the area – or have been raped or murdered.
"There are a lot of layers to this," says Harrington.
Authorities are looking into whether Matthew is connected to at least 10 rapes, murders and disappearances since 2002, when he was accused of a sexual assault at Liberty University in Lynchburg, Virginia. He was not charged because the prosecutor at the time "had no eyewitnesses or forensic evidence" – and because the complainant did not pursue charges, Lynchburg Deputy Commonwealth's Attorney Chuck Felmlee told PEOPLE.
Officials at Christopher Newport University in Newport News, Virginia, have also confirmed that they opened a disciplinary file on Matthew for a reported sexual assault in 2003, when he was a student there and a member of the football team.
"Students don't usually leave in the second month of the semester or leave the football team within a month," a university official stated in a press release.
Matthew attended CNU from January 2003 through Oct. 15, 2003. He was a member of the football team from Aug. 14 to Sept. 12, 2003.
Matthew's attorney, James Camblos, told NBC News that the "Commonwealth has yet to provide me with any evidence of links to those two cases," referring to Graham's disappearance and Harrington's homicide.
Camblos said he would not comment on any possible links to other unsolved cases in the area, including the 2005 sexual assault in Fairfax.
In the meantime, Matthew's friends are rallying around him, urging people to wait for all the evidence to come in before passing judgment.
"LJ," as he is known, "was a very friendly guy in high school and all of his female friends never felt anything but safe and protected around him," one of his friends from Monticello High School in Charlottesville tells PEOPLE.
"The person that we knew in high school and growing up – there's no way in any of our minds that this can be the same person accused of all these horrible things," the friend added. "It's almost the opposite of the person that we knew."