Why are the soviets to blame for a German massacre?

Oh yeah the massacre with polish bodies that misteriously popped up right on the borders with the USSR and where reported by nazi german soldiers and immediatly used by propaganda by the nazi goverments. Also why those reddit assholes cant see that even if the soviets did this massacre, why would they let the bodies so close to the borders that german soldiers would see? Nobody does this shit, its basically giving propaganda fuel for your enemy. Its so obvious the nazis did it and planted the bodies on the soviet border to create propaganda.