From the first time Gustav observed this street from the rooftop of the house he was invited in to take shelter, he noticed the dead bodies placed in basements of these buildings.
He recalled hearing the couple mention that the street in front used to be inhabited by citizens, but suddenly everyone living there disappeared, and they would occasionally see men in Red Jackets moving across the place.
Then the street became non-accessible, and everyone who tried going in never came back.
Gustav, at that time, didn't think much of it because he assumed Sahil instructed his henchmen to commit murder involving the people living in these households so he'd be able to use their houses as a storage center.
This was a war period, so the authorities who would usually handle situations like this were currently indisposed.
Even though Gustav felt this might have been the case, he wasn't so bothered for several reasons.