Born Hans Gareis in Frankfurt on November 7th, 1911; his father Joseph was a baritone at the opera theater there.
Hans studied conducting in Frankfurt, and worked as a répétiteur, still at the Frankfurt opera. At least occasionally, he sang on the radio as a tenor, without having studied voice. (A 1936 Berlin radio production of Schumann's Genoveva has survived, with Gareis in the small role of Caspar.) In 1938, he left Germany with his partner: he was gay, which was hardly compatible with life under the Nazi rule. They settled in Greece, where Gareis began to sing regularly and for a living, on the radio and in concert.
In 1940 or 1941, he and his partner emigrated to the USA, and Gareis worked as a répétiteur at the Met. His talent for singing was noticed, and in 1942, he made his debut as the First Knight in Parsifal, now as John Garris. He stayed in the troupe for the rest of his short life, as a comprimario: David, Mime in Siegfried, Cassio, Monostatos, Arturo in Lucia di Lammermoor, Narraboth, Walther von der Vogelweide, the Simpleton – a total of 316 performances in just seven years.
On a Met tour, the night train on which the troupe wanted to leave Atlanta was several hours late. A group of them wanted to eat something, the taxi that took them to the restaurant was too small, Garris said he would walk and join them. He never arrived at the restaurant, and the next morning (April 21st, 1949), he was found shot dead in an alley in downtown Atlanta. The police soon found out that he was gay, and that's where any serious interest in solving the case ended. The detective in charge was convinced Garris' death had to do with his "unnatural sexual activities" (the detective's words), investigated exclusively in that direction, without any fruitful results, and the case remained forever unsolved.
Reference 1, reference 2: Kutsch & Riemens