PHILADELPHIA (CBS) — On Friday, Capt. John Darby will end his 14-year leadership role as commander of the Philadelphia Police Department’s Special Victims Unit.

In an exclusive, one on one interview with Eyewitness News, the 36-year police veteran shared his thoughts.

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“The cases are disturbing, sobering,” Captain Darby told CBS 3. And there have been a lot of cases. More than 6,000 annually, meaning the Captain has handled more than 84,000 crimes.

Many of the investigations involve vicious attacks on the most vulnerable victims, including children. The veteran investigator says, as he leaves, he carries many of these cases in his heart.

“We do walk away with the effects of these cases from day to day,” he explained. “And there are the nagging cases that don’t get solved as well.”

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Capt. Darby says he had hoped to bring the Fairmount Park Rapist, who first struck 13 years ago to justice. But the predator, who has attacked 4 women, murdering one of them, remains on the loose, having last struck in 2007.

“I wish if I had my way, that case would have been solved before I walked out the door,” he said.

The Captain proudly showed off improvements in SVU making it easier for victims, including soothing murals hung on hallways near interview rooms where victims must share stories of the ordeals that often scar their lives forever.

When Capt. Darby does walk out the doors of SVU for the final time Friday, fellow officers say he will be remembered by them and by victims as a caring, tireless advocate.

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Asked what he hoped his professional epitaph might be, the Captain said quietly, “I just hope I can walk away saying we made things just a little bit better.”