Father Gareis was born in 1887 in Köhler. He was ordained in 1911/12. He served the parishes of Sewald and Husaren. He also served a parish in Kazakhstan before returning to the Volga where he served again in Husaren from 1925 to 1929. In 1929, he began serving the parish of Pfeifer. On 2 February 1930 he was arrested and accused of participation in a conspiracy group of German Catholic clergy. On 6 June 1931, following a trial by a secret police court, he was sentenced to three years in a concentration camp. This sentence was converted to a prison term and he was exiled to the prison in Tambov. In December 1934, he was arrested and again accused of being involved with the Catholic clergy conspiracy group. Following conviction during a secret trial that took place from 16-19 November 1935, he was sent to the Medveshya Gora concentration camp in the Kirov Region to work on the Baltic-White Sea Canal. He was sent there along with Alexander Staub, Josef Beilmann, and Josef Werbizkij. His exact fate is unknown, but it is assumed that he died there.
- Kurt Reinelt, Lebensbilder russlanddeutscher Märtyrer: Bischöfe und Priester; posted by the Germans from Russia Heritage Collection, North Dakota State University Libraries.
- Schnurr, Joseph. Die Kirchen und das Religiöse Leben der Russlanddeutschen - Katholischer Teil (Stuttgart, 1980), p. 369.