The hit was not penalized on the ice, even though it was interference at the least and a major/disqualification at worst.
According to a league press release, "Morley’s suspension is a result of a play at the 3:13 mark of the third period of Alaska’s game of Friday, Oct. 30 at Minnesota State, in which Morley made a blindside hit with contact to the head of a Mavericks’ player."
You can see it here:
The WCHA also suspended Alabama Huntsville's Brennan Saulnier for tonight's game at Lake Superior State because of "a play just under the 4:00 mark of the third period of Alabama Huntsville’s game of Friday, Oct. 30 at Lake Superior State, in which Saulnier made a contact hit to the head of a Lakers’ player."
Looking at the box score from that game, that hit, too, was not penalized. However, earlier in the game Saulnier received 5 minutes for roughing and a 10-minute misconduct — after scoring two goals, by the way.
The Morley hit on Mullin came while the Nanooks were short-handed, killing a 5-minute major/game misconduct to Josh Atkinson, who had hit Bryce Gervais in the head, possibly with his stick. Atkinson was not suspended. Both hits came in the game's final 3:05 when it was a 5-2 game and the Nanooks had been limited to one shot on goal in the period.