Despite keeping his alleged role in the war a secret in the United States, Karkoc is believed to have published a memoir in Ukraine in 1995, outlining his role in organizing and leading the Ukrainian Self Defense Legion in collaboration with the Nazis.
A British pharmacist who is an amateur historian researching the group came across the book and reached out to the AP for help tracking down Karkoc in the U.S.
Karkoc reportedly emigrated to the U.S. in 1949 with two sons after the death of his first wife. He settled in a Ukrainian neighborhood where he worked as a carpenter, remarried and had four more children, according to the AP.
"It doesn't come as a surprise," said Aaron Breitbart, a senior researcher at the Simon Weisenthal Foundation. "It is estimated that between 3,000 and 10,000 people entered the U.S. with dirty wartime pasts, who should not have been allowed in."
Breitbart indicated that Karkoc will likely not outlive the judicial process.
The U.S. doesn't try these alleged war criminals, but instead seeks to denaturalize and deport them. In some cases, foreign countries will ask for the suspect to be extradited.
In either case, the process is incredibly lengthy and can take years in court.
"It can take years and years by time courts say he can be deported," Breitbart said. "A good defense lawyer will drag it out until the guy gets biological amnesty. That is, until he dies."
Despite such suspects' advanced age, Breitbart said it remains important for governments to go after them.
"People need to know if you participate in a heinous crime, there is always someone looking for you," he said.