Here's a photograph taken in a similar position to the one above, on September 30, 2013; the current sign claims it was a "hall where the corpses were stored", and a place where executions frequently took place. No mentioned of how they were executed though.
This is a composite image (source) of the ex-alleged homicidal gas chamber, which was created with two video-stills (laid side-by-side) taken from Soviet footage of the remnants of the crematorium following the fire which destroyed the parts built from wood (i.e. most of it). The cameraman who shot this film was standing in a similar position to where I took the photograph above.