Kill the Punter

[parepat]

What do you think?

K lines up in punt formation. K1 (the punter) accepts the snap and punts the ball. After he punts his leg returns to the ground and takes a couple steps downfield while the ball is still in the air heading to R's receiver. R1 is lined up as a defensive end. He charges to try and block the punt. Knowing that he will not get to the punt he lays off and runs behind the punter. He then circles around and blocks the punter in the front and above the waist. The punter never saw him coming and is flattened. The block occurs approx 8 yards behind the LOS at K's 20.

Questions
1. Is there a foul on this play?
2. If yes, what is the foul? Why?
3. If yes, what is the enforcement?
4. If no, why?