Gallagher skates across the ice clearly lining up Pelech for a hit, but when Pelech skates by, Gallagher stops up and reaches his elbow out, making direct contact to the head of Pelech. He crashed to the ice clutching his head, left the game and has not since returned.
Gallagher received a match penalty for an intent to injure on the play, rightfully so. In addition to the harsh penalty on the ice, The NHL's Department of Player Safety will undoubtedly be reviewing this play, and Gallagher will likely be suspended for the first time in his 700+ game career.