What could this bug/beetle thing be?

"Carabid" is a scientific term for ground beetles, family Caribidae. They are varied in shape and coloration but most are darkly colored and shiny. They are usually fast moving predators of other insects such as caterpillars. Ground beetles are generally wary of humans and most species remain out of sight under rocks and debris during the day, but it is not uncommon for one to find its way into your house after coming to your porch light at night or looking for prey. Some of the larger species may bite if harassed but none are particularly aggressive towards humans that I know of and the vast majority prefer to scurry away when provoked rather than attack.