They look, first and foremost to be HDR, high dynamic range. That's a trick where you can use a digital camera to take multiple exposures of the same scene, altering the exposure for each one so that longer exposure reveal more detail in the darker or shadowy areas, while the shorter exposures show more detail in the well-lit parts without getting washed out.
Software combines the multiple exposures, so one image can show considerable shadowed detail but also clear well-lit detail, something that's usually not easy or even possible to do with a single exposure.
After that, he's further processed them by darkening key areas, notably the backgrounds. His aim was clearly to make them "loom" a bit more, to punch up the eerie, abandoned look.
So the result of heavily processing the images is to make them look... heavily processed.