In response to 50belowzero's comment:
They have to stick with the precedent of making absolutely no sense.
I guess the NHL can't believe one player can deliver 2 dangerous checks in one game. I don't think there's ever been a player who got 2 suspensions from 2 different checks in one game, and apparently the NHL's diciplinary arm didn't know how to deal with it. Sherriff Shanny didn't want to make a precedent.
Cool, so if you've thrown a suspendable hit, but somehow were not thrown out of the game, you've now got immunity until the horn sounds? Got it. Some specious interpretation of double jeopardy maybe...?
Whitey Bulger would love Shanahan. 'Excuse me, that murder came after I already killed someone else earlier that day -- you can't ding me for both!'