Hellinger was a Polish Jew, educated at several German universities, obtaining his doctorate from U Göttingen in 1907. In 1914 he was appointed Professor of Mathematics at U Frankfurt. In 1938 he was arrested (because he was a Jew) and taken to Dachau concentration camp. The following year he was allowed to emigrate to the USA, where he joined the faculty at Northwestern U.
http://findingaids.library.northwestern.edu/catalog/inu-ead-nua-archon-547 Web archive.