Warsaw, 11 May 1950. Janusz Gumkowski, acting as a member of the Main Commission for the Investigation of German Crimes in Poland, heard the person named below as a witness. The witness testified as follows:
| Name and surname | Konstanty Szymanowski |
| Date and place of birth | 24 October 1906 in Kazuń Polski |
| Names of parents | Jan and Józefa née Wojcieska |
| Occupation of the father | home-owner |
| State affiliation | Polish |
| Religious affiliation | Roman Catholic |
| Education | elementary school |
| Occupation | carpenter |
| Place of residence | Marii Kazimiery Street 13, flat 1 |
| Criminal record | none |
When the Warsaw Uprising broke out I was at Marii Kazimiery Street 13. On the first day of the Uprising, the Germans, or more precisely the Wehrmacht troops from the Gas School at Gdańska Street 6 (where they had been stationed since 1939 or 1940), set fire to houses in the vicinity of the school, hence numbers 5, 9, 11 and 13, and on the other side of Marii Kazimiery Street, numbers from 18 down. Then I moved to the adjacent house at Marii Kazimiery Street 15, where I remained until 14 September 1944. During this entire time we couldn’t move freely in the streets as the area was constantly under fire from the Germans stationed in the barracks at the foot of the hill with the church of the Queen of the Polish Crown on top.
On 28 August, the Germans announced over loudspeakers that everyone in our area should leave Marii Kazimiery Street and the neighboring streets that day, heading towards the Central Institute of Physical Education. Those who didn’t obey would be considered bandits and executed. Some inhabitants did as ordered, but many people stayed. On 14 September 1944, at around 4.00 p.m., German tanks entered our street. The main attack on Żoliborz had been launched. The Germans forced civilians from the houses on Marii Kazimiery Street and neighboring streets – Dębińskiego Street, Rymkiewicza Street. Some people were executed on the spot, beside their houses, and the houses were then set on fire, and some people were led in the direction of the Central Institute of Physical Education; the men were executed along the way, in Wolańska’s garden at Marii Kazimiery Street 70.
The civilians from the house at Rymkiewicza Street 3 where I was at the time, some 40 people, were taken by the Germans to the empty lot in front of the then already abandoned Gas School. When we reached the barracks, the German soldiers began to shoot at us. I was injured and fell. After the execution, the Germans left in the direction of lower Żoliborz. In the evening, I got up and hid in the barracks. The following day, I went to my house at Marii Kazimiery Street 13, where I remained in hiding for three days.
Some 33 people were killed in the execution of civilians carried out by the Germans on 14 September 1944 in the vicinity of the barracks (the Gas School). Apart from me, the following people survived the execution: Kornela Wysocka (domiciled at Rymkiewicza Street 3, flat 7), my son Andrzej (domiciled with me), Buczyński (domiciled in Wrocław), Zofia Ignaczewska (I don’t know her address, she has recently married). In total, some 14 people survived.
In the spring of 1945, the Polish Red Cross carried out an exhumation of the grave of the victims of that execution.
How many people might have been killed in our area that day, 14 September 1944, I cannot say exactly. I think, however, that it might have been about a thousand people.
At that the report was concluded and read out.