At the end of the first period of the game between the Montreal Canadiens and Philadelphia Flyers, P.K. Subban and Brayden Schenn engaged in a protracted physical battle along the boards. It nearly turned into a fight after a big hit between the two, but things didn't really come to a head until after the horn sounded for the end of the period.
Here are a few angles of the incident, with commentary from the various broadcast teams covering the game:
At full speed, it can be tough to tell exactly what is going on here, but watching the replay, it seems fairly obvious that Subban is trying to draw a penalty by collapsing after Schenn pushes him up against the boards.
Schenn took the only penalty on the play, for unsportsmanlike conduct.
(Video from HockeyVideoHD)