This man is an Officer (Sotnik or US Lieutenant) of the HIM Cossack's Convoy Regiment, Uzik Zborovsky. He committed suicide in 1916.
Good grief Nicolá , is it known why? The War? was he badly wounded?

Some corrections about this interesting man. I firstly mistaken about his "suicide". Thank to the person with nickname "cosser" across the Russian internet. Btw, Demenkov's confusion with Butakov is also him/her "work"

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Zborowski Victor Erastovich (1889 - 9. 10. 1944, Austria). Russian Officer, WWI and White Guard military commander. Fought on the Nazi's side against the USSR. Major General during WWII (Oberst). Holder of the Iron Cross (received just before his death from the injuries).
Born in 1889 in Cuban. Graduated from the Moscow Kadet Corps and Nicholas Military school. From 1912, Officer of the HIM Cossack Convoy. Fought in the WWI where was seriously injured. Treated in the Tsarskoe of GD hospital. Participated in the Rus. Civil War on the White's side in different positions, Regiments and with different ranks, from Sotnik to Colonel (commanded HIM Convoy in 1920). Emigrated to Yugoslavia.
And the most interesting: in December of 1941 joined the Russian Corps in Serbia. Corps fought against the USSR and Yugoslav partisans on the Axis side. Commanded the 1st Cossack Regiment. Participated in the different serious battles and was deadly injured in 1944. Received Iron Cross just before his dead. Later 1st Cossack Regiment was named after him. Buried in Graz.