Keeping the beetles out of your home is not the easiest thing to do. You need to make sure that every door threshold sealed 100%, that all of your weather stripping on your doors and windows is intact and that there are no holes in your screens because many species are attracted to lights.
The more I think about it the more I think you are likely to have ground beetles.
Ground beetles belong to the family Carabidae, one of the largest beetle families. The adults vary in length from about 0.1 inch to more than 1 inch. They are usually dark colored, often shiny and somewhat flattened. They tend to be most active at night, with some species highly attracted to lights. During the day they are found under objects on the ground. They are fast runners and it is common to see them moving quickly along the ground.
Indoors, they tend to seek hiding places under boxes or other objects on the floor, particularly in moist places such as basements. Though they invading homes three during seasons, they tend to be most active during the time of year when nighttime temperatures drop. The larval stages occur outdoors in the same surroundings as adults, but adults and larvae are not necessarily found together. Both adults and larvae feed primarily on other insects. Because they are predators, they should be considered beneficial.
When ground beetles enter homes, it is an accidental invasion. They cannot survive and reproduce there.
Control measures indoors usually are not necessary except to hand-pick or vacuum the beetles and return them outdoors. Removing rocks, boards or other objects that ground beetles may hide under from around outside walls discourages beetle accumulation near the home. Caulking cracks and making sure that doors and basement windows fit snugly also helps prevent entry.
To help prevent ground beetles from entering homes, spray 2 to 3 feet of the foundation from the ground up, and treat a band around the house from the foundation out about 5 to 10 feet. For these purposes, use a spray of 0.5 percent diazinon or 0.5 percent chlorpyrifos (Dursban®).
Some excerpts of the above by:
Darryl P. Sanders - Department of Entomology - University of Missouri