Here's a for-instance: if someone with a lot of rage and a gun shoots people as they wait in line for a movie, we might say that the victims were in the wrong place at the wrong time. This isn't our way of saying that it's their own damn fault for wanting to see a movie. It's our way of saying that they happened to be the humans nearby when someone started shooting.
So this guy with a lot of rage just happened to start shooting his gun, and he just happened to be at their home, and they just happened to be the humans nearby (at their home) when he started shooting. Wrong place, wrong time.