It took police three years to arrest the man who killed Shannon Shannon Schieber, a 23-year-old business school student, in 1998

A 23-year-old business student from Maryland was found naked, raped and strangled to death inside her Philadelphia apartment in the spring of 1998.

A critical break in the case didn’t come until three years later: DNA evidence would eventually connect serial rapist Troy Graves with Shannon Schieber’s brutal slaying and the sexual assaults of five other women in Philadelphia. Graves was arrested in Colorado in 2001 and, after pleading guilty to his crimes in Colorado and Pennsylvania, he was eventually sentenced to life in prison.

The stalking and killing of Schieber and the investigation that led to Graves is the subject of tonight’s episode of People Magazine Investigates. Titled “Terror in Philadelphia,” the episode airs on ID tonight at 10 p.m. ET. An exclusive clip about the investigation is shown above.

In the clip, former Philadelphia District Attorney Lynne Abraham, who ultimately brought Graves to justice, speaks about the mood in the city during the serial rapist’s rampage.

Shannon Schieber: in duke seatshirtcredit: Courtesy Schieber Family
Shannon Schieber
| Credit: Courtesy Schieber Family

“Women in town were just absolutely freaking out,” Abraham recalls.

The clip also shows Chuck Boyle, a retired Philadelphia detective, and Vicki Schieber, Shannon’s mother, who still can’t comprehend why anyone would want to hurt her daughter.

“How could somebody do that?” she wonders.

• For more on this story, watch “Terror in Philadelphia,” the latest episode of People Magazine Investigates, airing tonight at 10 p.m. ET on Investigation Discovery.

After her body was found, police were heavily scrutinized for their initial handling of a call to Schieber’s apartment.

A neighbor, Parmatha Greeley, called 911 after being awakened by screams of “Help me! Help me!” He ran to Schieber’s apartment, pounded on the door and shouted that he was calling police. “I just heard like a choking sound,” he told the 911 operator.

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Within seven minutes, two policemen were at Schieber’s door, but they left after they knocked on the door and got no answer.

“The hardest thing to accept, is that our daughter did everything she could to call for help,” Syl Schieber, Shannon’s now 72-year-old father, told PEOPLE in 1999, soon after filing an unsuccessful lawsuit against the city and its police.

“Shannon was a good person who went out of her way to help almost anyone,” he added. “The one time she needed help, the system didn’t work.”

People Magazine Investigates: Terror in Philadelphia airs tonight at 10 p.m. ET on Investigation Discovery.