Many concentration camp inmates say in their memoirs that one of the most tragic aspects of the Holocaust was that its pawns often became the prisoners themselves. In order to maintain order in the camps, the Germans used so-called functionary prisoners, including overseers, managers or foremen known as “kapos“. In most camps, such functions were given to German criminal prisoners, but this was not the rule, as functionary prisoners also became representatives of other nationalities. There were various reasons for this, they could be, for example, acquaintances or speaking German.

Ostrowski was arrested in Łódź in the spring of 1940 by the Gestapo. He was initially held in the local prison, but after a few months he was sent to the Radogoszcz transit camp, a stop on the road to forced population resettlement. Ostrowski was taken to another prison in 1942. He managed to escape from it, but what happened to him over the next two years is unknown. In 1944 he was arrested by the Gestapo in Berlin, and in October 1944 he was sent first to the prison in Moabit (now Berlin), then to the Gross-Rosen camps, from where he was sent to Mittelbau-Dora, and finally on April 10 he was sent to Bergen-Belsen. In the latter he lived to see his liberation from the Nazis.

However, the arrival of the British did not mean freedom for Ostrowski, as he was arrested as a suspected member of the camp crew. The first trial of the Bergen-Belsen crew lasted from October 17 to November 17, 1945, and Ostrowski was tried there along with Josef Kramer or Irma Grese. During the trial, several prisoners stated that they recognized Ostrowski as a kapo who repeatedly beat and abused other prisoners. In the trial file, one can read the testimony of Soviet prisoner Vladimir Sulima:

In the Dora camp, I saw Ostrowski beating many prisoners every day. When we went to work digging deep tunnels, Ostrowski did not work and stayed in the barracks (…) When we finished work we returned hungry, Ostrowski repeatedly refused food to some, and gave little to others.

Ostrowski was accused of similar wrongs by two Soviet prisoners, Nikolai Kalenikov and Andreg Nykrasov. In a written statement, they further testified that Ostrowski became a block officer at Bergen-Belsen, who instituted corporal punishment for the entire block and refused to give food to prisoners. In turn, Peter Ivanov testified that he heard from other prisoners that Ostrowski had beaten a French prisoner to death the day before the camp was liberated.

During his testimony, Ostrowski denied all the accusations. He claimed that he himself worked in the tunnels while in the Dora camp, denying that he was a kapo. He admitted that he had been a shtub [a functionary prisoner in charge of cleanliness in a part of the barracks] at the Dora camp, following his accident while working in the tunnels. In Bergen-Belsen, on the other hand, he had been a prisoner in Bergen-Belsen for too short a time to be given a position as a function prisoner. He also testified that after arriving at the camp he was sick and spent most of his time in the barracks next to the camp, where he himself had a conflict with a block senior (from German: Blockältester) and what he was accused of having done was committed by the block.

The court did not believe Ostrowski, who was sentenced to 15 years in prison. He left prison in June 1955. It is not known what happened to him thereafter.