It lives there or just get in for a visit. Most of time they just get in for the garbage, not a problem as long as they don't stay there. You kill one, another one would move in notime.
I honest don't think killing them is neccessary, they do no harm and they just found a wrong shelter. You can simply remove them, put them in a box and release them at a park. If you don't want to come in contact with them yourself, please call animal control or Ottawa Humane Society, they will come take them and release them in the wild. Let's share the planet Earth with wildlife in harmony.