Before this playoff series even started Sheldon Keefe warned that he expected the series to be borderline violent. It's already pretty clear he undersold the series. After Kyle Clifford was ejected on the 1st period things were pretty tame until the 3rd period.
With the Maple Leafs leading the game 5-0, Corey Perry and Pat Maroon attempted to convince Wayne Simmonds to drop the gloves. But being the veteran he is, Simmonds knew there was no value dropping the gloves in that situation, but that didn't stop both men from trying.
After the play though as cameras cut to commerical things escalated and every player on the ice for involved in the play.