That's a Timber Rattlesnake, dark form, Crotalus horridus, appears to have had part of its rattle broken off. A rather harmless snake, the bite usually swells the immediate area, which goes away in a few weeks, usually two. An antivenom is available, but is usually more dangerous than the snake. In other words, should of left it alive to kill rats and mice. And no, I'm not starting a company. Snakes belong outdoors, where they can control the pest populations.
