Virginia Tech student Morgan Harrington disappeared in October 2009 after attending a concert at the University of Virginia in Charlottesville. Her body was found three months later on a remote farm, 10 miles outside the college town. On Sept. 29, Virginia State Police announced that it had found forensic evidence linking Jesse Leroy Matthew, Jr., the suspect in UVA sophomore Hannah Graham's disappearance, to Morgan, providing a "significant break" in her case.
"With one blow, the killer injured us grievously by murdering Morgan," Harrington, 57, tells PEOPLE. "But I was determined to limit his damage to that one blow. The strain of this kind of catastrophic event causes marriages to fail and breaks relationships apart. I was not going to let him do that with my marriage to Dan or with my son. I was also determined to make something good come from Morgan's death."
Remembering MorganSince 2004, Harrington has been working with the non-profit Orphan Medical Network International helping to provide schooling, hot meals and medical care to people in Zambia, Africa as a tribute to her daughter – and helped to build a school in 2012 in Morgan's name.
"Morgan, who wanted to become a teacher, was determined that she and her good friends would come and work with me in Zambia once she graduated from Virginia Tech," Harrington says.
Courtesy Gil Harrington
"Morgan can't go to Africa and can’t teach because she is dead," she says. "Despite her death, many children will be educated in her honor. That’s her legacy."
One of Morgan's closest friends, Erin Cole, is honoring Morgan by helping as well, Harrington says.
"Erin raised the majority of funding to build the school by holding a golf tournament in Morgan's name, though she was just 20," says Harrington. "She later came with me to Africa, working with me and the OMNI team. She did it all for Morgan. That was her way of honoring her murdered friend."
Harrington, who is trained as an oncology nurse, also works with OMNI to provide medical care in Zambia, traveling there at least once a year.
"It's a privilege to be able to look people one by one in the eyes and help them," she says.
Saving the Next GirlIn 2010, Harrington and her husband, Dan, started a non-profit organization called Help Save the Next Girl to help promote personal safety among young women.
"I wanted to save the next girl from being murdered in Charlottesville," says Harrington, who has also joined in the search for Graham.
Even though she has helped saved lives in Zambia, Harrington says she gets more from helping people than they get from her.
"Some good had to come out of Morgan's murder because she was good," she says. "Doing good in the world – that's how you trump evil."
For more on the Hannah Graham case and Morgan Harrington's murder investigation, pick up this week's issue of PEOPLE, on newsstands Friday