Shadows moving at inhuman speed.

This happened about an hour ago, as I was driving to work.

I saw a shadow dart across the road, faster than any rabbit, deer, or human ever could. But it didn't just keep going, I saw it come back into my view, bend down as if it dropped something, then take off again.

This happened two more times on the hour commute I have, except the shadows just kept going instead of doubling back. I've seen shadow people before, but nothing like this. Amy ideas??