Solving My Best Friend's Murder: How a Stay-at-Home Mom Became a Private Investigator to Crack a Cold Case

In 2004, Sheila Wysocki was a stay-at-home mother-of-two in Nashville, Tennessee, more concerned with neighborhood cookie exchanges than murder and rape cases – let alone trying to solve them.

But that changed one afternoon when, she says, she glimpsed the ghost of her college roommate, Angie Samota, standing at the edge of her bed. Samota was brutally murdered and raped in 1984 and her case had gone unsolved for more than two decades.

"I know it sounds crazy," Wysocki tells PEOPLE in an article that appears in this week's issue. "I promise you that it sounds crazy to me."

What happened next was even more out of the ordinary: In a flash, Wysocki "knew it was time" for either her or the authorities to finally track down the killer of Samota, who was a sophomore at Southern Methodist University at the time of her murder.

For more on Sheila Wysocki and her work on cold cases, pick up this week's issue of PEOPLE on newsstands Friday.

She picked up the phone and called detectives at the Dallas Dolice Department to ask about the case – but was promptly given the brush off.

Four years and more "over 750 phone calls" later, Wysocki goaded detectives into locating their supposedly "lost" crime scene evidence. The evidence, it turned out, contained DNA from Samota's killer – serial rapist Donald Bess, who was eventually convicted and sentenced to death in 2010.

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"You want to make me mad?" says Wysocki, 53, who got her private investigator license after she felt police had lost interest in Samota's case. "Ignore my phone calls."

Now, the mother-of-two has taken the investigative skills she learned while immersing herself in her friend's homicide and put them to use in other cold cases, ranging from murder to rape.

Many of her clients are the victims' mothers, who she says have "been beaten down by the system," but remain desperate to learn the truth about the deaths of their children.

"Angie was the type of friend who stood up for others," says Wysocki, the mother of two grown sons. "And that's really all I'm doing now."