The cold-case murder of an 8-year-old Chicago girl that remained a mystery for over 65 years was finally cracked with the help of new DNA technology — and her killer turned out to be one of the very people who was supposed to protect her, a cop.

New DNA evidence gathered from a genetic ancestry website led Chicago Police Department investigators to suspect former Chicago homicide detective Thomas Francis McInerney was responsible for the death of little Gloria Kowalewicz on Nov. 12, 1960, the Chicago Tribune reported.

Former cop Thomas Francis McInerney was linked to the cold-case murder through DNA testing and a fingerprint match. Chicago Police Department

Gloria’s murder shocked the Windy City more than six decades ago after her body was found in a ravine miles from her family’s West Englewood home. She had been shot twice in the head.

The little girl was last seen starting off from home on a short walk to a nearby church in order to receive communion. 

The shocking murder ignited a massive manhunt for the killer by local and state police, as well as volunteer help from local firefighters, Boy Scouts and veterans, the Tribune reported. 

Investigators made some progress – deducing that Gloria hadn’t been killed until she was taken to nearby woods and collecting eyewitness reports of a little girl seen with a young man, but they hadn’t been able to identify a suspect.

The investigation was finally broken open earlier this year, the outlet reported, after the FBI was able to connect McInerney, who was 24 at the time, to the crime scene thanks to DNA submitted to a family tree website. 

Gloria Kowalewicz’s murder shocked the Windy City more than 65 years ago after she was found shot twice in the head in a ravine miles from her family’s West Englewood home. Find a grave.com

Further testing of DNA, fingerprints and ballistics led the department to conclude that McInerney, an Army veteran who lived around the corner from Gloria, was responsible for the little girl’s death. 

CPD’s Chief of Detectives Kevin Bruno praised the dedication of investigators who’d worked tirelessly on the case for over six decades, telling the Tribune it was proof “we don’t forget.” 

“The fact that he was a police officer is deeply troubling to all of us that have made a career out of this most noble profession,” Bruno told the outlet. “But at the same time, it’s not something we’re going to minimize or shy away from.”

Gloria’s brother Adam Kowalewicz said that he was relieved that his sister’s killer had been identified, and had hoped it would allow his parents, who have since passed, to “rest.”

Still, Kowalewicz is frustrated that McInerney, who died in 2006, was able to escape justice for his actions. 

“He never paid his dues,” Kowalewicz told the Tribune. “You hope he’s going to pay his dues with the good lord.” 

McInerney was on the Chicago police force for 28 years and then worked for the Federal Public Defender’s Office in both Las Vegas and Reno as an investigator until retiring in 2004, according to an online obituary. He was named Outstanding Federal Defender Investigator in 2003.

Family for McInerney, who was a dad of five — including three daughters — and grandfather of many, could not be reached for comment.