In cities that allow mixed races to settle, imps will move in regularly as well for various reasons. However, due to their appearance and the lifestyle of goblinoids in general (being facultative nocturnal and preferrance for climbing rather than staying on the ground), a significant portion of them remains at the bottom of society. These particular groups tend to form their own subcultures and while some prefer to live as scavengers, illegal activities are not uncommon, much to the chagrin of the individuals living by the law.
What exactly is going on here I will leave to your imagination. It could be a planned robbery or murder, but it's also quite possible they are chasing the guy away. In the latter case it likely won't be a smooth process for the ones inside those houses, since being expert sound imitators, imps are able to produce a screech at the resonance frequency of a human's ear. Imagine the sound of finernails on chalkboard, only louder and not ending.