The spider pictured here was found in my second-story office, but I suspect it had somehow wandered into the house and was not in its native habitat. I have seen other specimens as well, so perhaps they do make a habit of hunting forays indoors?

The ground spiders (family Gnaphosidae) include nearly 2,000 described species in over 100 genera worldwide. Ground spiders are characterized by their longer cylindrical anterior spinnerets being far enough apart that the median spinners are visible. 

Ground spiders do not build webs for prey capture, but are active nocturnal hunters, mostly of other spiders. [1] They chase down their prey much like the wolf spiders (family Lycosidae) or the jumping spiders (family Salticidae).  They spend the day in a silken retreat. The thick-walled egg sacs are guarded by the mother until the spiderlings hatch. [3]