Tyler Seguin scored two shootout goals in Boston's 2-1 victory over New Jersey. Unfortunately for Seguin, only one actually counted as the first was waved off after a fan tossed a piece of debris on the ice as he was shooting. While the trash didn't appear to interfere with the play, Seguin had to take his shot over again. He buried it - again - much to the delight of the Boston faithful.
It's unclear whether the guilty fan was rooting for Boston or for New Jersey (the game was played in Boston), but it's hard to imagine why someone would think chucking something on the ice during the shootout was a wise idea. It's safe to assume the guilty party probably enjoyed a few drinks at some point during the night and was severely lacking common sense and respect for the game.
One of the first rules of attending a sporting event is that you never should throw things on the playing surface, with a few notable exceptions - hats for a hat trick, a homerun ball from a visitor, etc. In hockey, there's rarely an acceptable time aside from the previously mentioned hats and teddy bears during the infamous teddy bear toss. All of these instances take place after the whistle. It's never appropriate to interfere with the game.