Due to the swift progress of the German offensive, the NKVD began exterminating political prisoners in the war zone.

In the summer of 1941, in the part of Poland occupied by the USSR, an estimated 20,000 to 30,000 individuals were murdered in prisons and detention centers.

[4] This information is also found in the "List of departures and movements of transports from NKVD prisons of the Ukrainian SSR".

[5] After the outbreak of the German-Soviet war, militants of the Organization of Ukrainian Nationalists (OUN) made an unsuccessful attempt to capture the prison.

The witness cited by Węgierski reported that initially the bodies of the victims were taken outside the prison and buried in previously dug pits.

Another 40 bodies were to be transported from the prison by cars, but as a result of a Luftwaffe air raid, they were abandoned along with the vehicles on the road.

Filippov claimed that the prison warden and his men later tried to bury the bodies left behind, but due to another raid, they only had time to throw them from the cars.

The soldiers threw grenades into basements where civilians were hiding, and for unclear reasons, they also took hostages from among the local population – including women and children – whom they later murdered on the Berezhany–Shybalyn road.

As per the antisemitic canard of Jewish Bolshevism, non-Jewish inhabitants perceived Jews as synonymous with the Soviet regime and its policies of terror.

After the Germans took control of Berezhany, which happened on July 4, 1941, dozens of local Jews were forced to work on the exhumation and burial of the corpses of murdered prisoners.