The site is actually fairly typical of what happened during Stalin’s Great Purge, in which at least 750,000 Soviet denizens were murdered. After Vladimir Lenin’s death in 1924, Joseph Stalin quickly ascended through the ranks, eventually declaring himself dictator in 1929. And Stalin considered any residual support for Lenin or his Bolshevik party to be a threat to his authority, so he tasked the NKVD with eliminating anyone even suspected of being a threat.

In addition to the deaths of nearly a million people — including an estimated one-third of the Communist Party itself — the Great Purge sent millions more to Gulag labor camps, where many of them died. At its height, the Great Purge went after not only men suspected of disloyalty but also their families, including wives and children as young as 12. After Stalin’s death, his successor, Nikita Khrushchev, condemned the Purge and admitted many of its victims were innocent (via History).

As with many of the Purge’s mass graves, the motive for and extent of the violence that occurred at Odessa is unlikely to ever be truly known. According to All That’s Interesting, the grave extends onto military land and lies beneath buried wires; further, any records of the mass execution are held in Moscow and remain classified.