I had a quick read of the German page you linked to. What I gathered from the text is that the author was brought to the Butzweilerhof airfield on the morning after the attack on Köln to assist in identifying bodies. He assisted in determining the identity of a body that was found in the rear turret of a Lancaster that had crashed on the field, most likely having been shot down by Flak (ND388). An ID card found on the body in a pouch below his sweater confirmed that this was 22 year old M.A. Krewenchuk. It is not clear to the author why they were asked to assist in this, the Bergungscommando took care of the rest. The author was 16 years old at the time and has since visited Krewenchuk's grave, the photo on the page showing the headstone was taken by him in 2008. He mentions in the text that Christmas was definitively over for him after that encounter.