What to do with an Alligator Snapping Turtle?

I went out today and when I was coming out of the building I was in, I found a small turtle, maybe the size of a half dollar, in the parking lot. I was not sure what kind of turtle it was until I brought to a pet store near by where they told me it was a snapper. One of the employees gave me a small container filled with shallow water and holes for air on the plastic top. Just a moments ago I realized I had an ALLIGATOR SNAPPING TURTLE next to me! I'm not sure now if I should be releasing it into a nearby swamp, keeping it, or selling it? If I do keep it would anyone be able to tell me how to properly take care of it? Or are they to dangerous to keep as pets? I know close to nothing about them. Also I found I live in New York, and I found the Turtle in New York, are they indigenous to this area?