John Skelton was just trying to throw the ball away. Nobody was open, and Skelton was just trying to deliver the ball to the Seahawks bench, but Richard Sherman had other ideas. The result was an amazing interception.
Look at Sherman's body control as he makes the catch.
The play was reviewed and confirmed. A reverse angle showed him dragging his toes, just barely, as he fell out of bounds. It might just be the best interception you see in quite a while.