Hmm... all of the answers seem pretty similar really.

I have been in a pretty similar situation reffing where I saw the foul (though this one was on the player with the puck) and was waving my hand when the second player retaliated by pushing the other player. What I did was:
- Stop the play (of course)
- Give a free puck to the team that was fouled first
- Kick the player who committed the first foul out for 2 minutes (was 30 min game)
- Explain to the player who was fouled that I had seen it, and was calling it. Then give him 2 minutes also for the reaction. This in a loud enough voice that his team know that he reacted and that is why he is going to the bin.
- Reverse the free puck.

Not sure if that is completely according to the book, but there you go.

Kyusap - one thing though: you did well to see the original foul. A lot, an awful lot, of referees are so focused on the puck that they are blind to anything that happens 2 m away from it.
If they got ancy after the game and wanted to argue with you about it, then you should refer them to Duck. He will sort them out.

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Faster than a speeding puck...