He got punched in the face. What else would he have done? And what could the players on the ice have done differently? There were 6 Blues forwards one the ice and all of them had a Wing tied up, leaving the 6th guy on Howard.
I don't like that those were the players out there, but what exactly is Howard supposed to do differently when he gets suckere punched in the face?
Just analyzed the replay.
Petro didn't look like he made contact with Howard when he took a swing, if he did he just grazed his shoulder, maybe the side of his mask...but he wasn't sucker punched. And it looked like the puck came up, Howard had it on his chest, may have been fluttering a bit, Petro took a swing that goes over Howard's shoulder...maybe he's swinging at the puck trying to punch it in, not sure what he was doing because you lose sight of the puck from that camera angle.
Honestly, if he wanted to sucker punch him, he could have easily done so.
Either that, or he is a horrible fighter with terrible aim.