"...they slice his belly open,
tear his intestines out
and stuff a dead dog inside..."

This procedure seems to have been popular with the Eastern peoples in general; the Poles were not the only ones who desecrated their victims in this way. The literature on the expulsion of the Sudeten Germans from Czechoslovakia in 1945 also repeatedly mentions this technique - see, for example, the book Sudeten German Inferno by Ingomar Pust, specifically here.)