More than 65 years of searching for a killer has ended: Chicago police say they now know who shot an 8-year-old girl walking to mass.

He was part of the force.

Chicago cop Thomas F. McInerney Jr. has been identified as the man who abducted, shot and killed Gloria Kowalewicz on Nov. 12, 1960.

At the time, McInerney was a recent addition to the agency, a violent crimes detective with the Chicago Police Department. He died in 2006.

But evidence pointing to him as the killer lived on. And recent improvements in technology finally brought answers.

Just before 8 a.m. on the morning of her death, Kowalewicz began walking a few blocks from her home to St. Mary of Mt. Carmel Church. She never arrived.

About four hours later, her body was found in a ditch in a forest preserve southwest of Chicago. Her killer left evidence scattered at the scene of the crime and along a highway back to Chicago.

Investigators found a bullet, Kowalewicz’s coat, her shoes, and her little, white communion purse that held her prayer book. But the killer was never identified.

But recently, investigators pursued more clues using updated technology. Ultimately, it was a fingerprint lifted off the strap of her purse that led investigators to McInerney after more than six decades.

As part of the investigation, Chicago police formed a task force. They knocked on hundreds of doors and interviewed more than 1,300 people in the hopes of finding the girl's killer.

More than a dozen people were questioned under a polygraph. The man responsible continued to blend inside the department.

"It's not that law enforcement was incompetent at the time—they just didn't have the sophisticated investigative tools," said Michael Gould, a founding member of the New York Police Department’s K-9 unit.

Using K-9 teams to track the scent of the killer could have been a more effective strategy, Gould told Fox News Digital.

But using dogs to investigate crimes wasn’t widely adopted until the mid ‘80s, Gould said. Now, they’re routinely used and have "cracked a lot of missing person cases."

"Dogs could have tracked where the person lived and what direction he fled."

"They give us X-ray vision. They allow us to see things—evidence—that's invisible to the naked eye. And that's what the primary locating tool should be for law enforcement, police K-9."

Chicago Police Department detectives never stopped searching for the girl’s killer, according to a statement sent by the agency to Fox News Digital. Through the years, they worked with Illinois State Police and the FBI to continue a quest for answers.

The DNA and fingerprint evidence was preserved for decades until, finally, technology advanced enough to bring answers.

It’s rare for law enforcement to maintain records and keep evidence that long, Gould said.

He expects the DNA connection may lead to solving more cold cases.

"My prediction there are going to be other victims [linked to McInerney]. I don't think this was a sole act."

"This, in my view, would have been a planned and intentional act. It's rare that this happens once in a serial murderer's life," he said. "They don't do it one time. In fact, it usually escalates when they're successful."

What makes it "even more horrific," Gould said, is that McInerney may have used his influence as an officer to lure her into his car.

"We teach our children that you should trust law enforcement, and when they leverage that against innocent people, particularly children, it's horrendous."

After working in the Chicago Police Department for 28 years, McInerney retired and moved to Las Vegas. He died 20 years ago at age 70.

"His abhorrent actions not only took the life of an 8-year-old child, but left her parents and all who knew and loved her shattered as they searched for answers," the Chicago Police Department said in a prepared statement.

"McInerney should never have worn the CPD star, and it is devastating to accept that he was never identified and held accountable while he was alive. Though her parents have since passed away and were not able to receive justice in their daughter’s murder, we hope that this news brings a measure of closure to all who knew Gloria and her story."

The Kowalewicz family’s spokeswoman, their attorney, did not respond to requests for comment from Fox News Digital.