German authorities have opened a war crimes investigation against Johann “Hans” Breyer, a former Nazi camp guard who has been living in the United States for 60 years.

Breyer, an 87 year old retired toolmaker living in Philadelphia, admits to having been a guard at the Auschwitz death camp, but claims that his post was outside the camp and that he had nothing to do with the horrors that occurred within its gates.

“He was a trained, paid, uniformed armed Nazi guard who patrolled the perimeters of two such camps with orders to shoot those who tried to escape,” a court ruled in 1994, according to CNN.

For years the U.S. has been trying to revoke his citizenship, but Breyer, who emigrated to the United States in 1952 and claimed citizenship as a displaced person, won his fight to remain in the country in 2003. The court ruled that he was not responsible for having joined a Nazi unit because he was only 17 years old at the time.

German authorities are investigating evidence against him, and expect to have preliminary results in October, according to Gert Schaefer, a spokesman for the chief public prosecutor in the Bavarian town of Weiden.