I bought the whole thing until the heel kick. I see that play happen a lot. What I don't see are guys kicking their heel right into another player.
So Matt Cooke losing balance while leaning into someone along the boards, while standing on one leg isn't plausible? I understand it's Matt Cooke, but he's only human, and that play sure seemed accidental to me. He tried to get his knee between Karlsson's legs and then plant, instead of planting between Karlsson's legs, he planted on Karlsson's leg that he just got into position.
The whole play was so short, if Karlsson's legs didn't get moved together Matt Cooke would have been able to plant his foot on the ice pinning Karlsson to the boards, but in less than a second Karlsson had his legs come together and Matt Cooke was just finishing the play like any normal hockey player would. It's a terrible accident, but this isn't a situation where Cooke saw someone vulnerable on the ice, skated up, and the jumped on his leg. This play was completely normal, and would have been without tragedy if Karlsson legs stayed apart which is much more common along the boards, rather then jumping and keeping your legs together.