(CNN) -- A suspected Nazi war criminal died in Philadelphia overnight Tuesday, just hours before a U.S. court ruling cleared the way for him to be extradited to Germany to face trial.
Johann Breyer, 89, died at Thomas Jefferson University Hospital of unknown causes, according to James Burke of the U.S. Marshals Service.
On Wednesday, U.S. Magistrate Judge Timothy Rice granted the U.S. government's request for an extradition certification "based on Breyer's role as a Nazi 'Death's Head Guard,' in the murder of 216,000 European Jews at the Auschwitz II-Birkenau death camp" and one other location from 1943 to 1945.
"As outlined by Germany, a death camp guard such as Breyer could not have served at Auschwitz during the peak of the Nazi reign of terror in 1944 without knowing that hundreds of thousands of human beings were being brutally slaughtered in gas chambers and then burned on site," Judge Rice said in court documents released Wednesday.
He was facing 158 counts of contributing to murder, one charge for each trainload of European Jews who were forcibly deported to Auschwitz, in southern Poland, between May and October 1944, according to court documents.
Breyer's attorney was not immediately available for comment Wednesday. An exact extradition date had not been set.
Breyer was arrested in Philadelphia last month and held without bail. He was awaiting the extradition hearing when his health deteriorated and he was transferred to the hospital on Saturday.
He had lived in the United States since the 1950s, most recently with his family in a red brick row house in northeast Philadelphia.
The U.S. case against Breyer dates to the 1990s, when federal authorities sought to strip him of his U.S. citizenship, arguing that Nazis were not eligible.
Breyer maintained his citizenship, however, after he was able to establish that his mother was born in Pennsylvania and returned to Germany before World War I. After World War II, Breyer migrated to the United States in 1952 and claimed citizenship as a displaced person.
Authorities alleged that he admitted to serving as a guard but deliberately made false statements to minimize his role in the Holocaust.
CNN's Julia Talanova contributed to this report.