Let's all hope for the sake of the industry and aviation that it wasn't another intentional collision with a building. Regardless of who it might have been or their motivations, if it does turn out to be an "attack", more useless legislation that does nothing to secure aviation (and only hurts law abiding aviators) is sure to follow.
That said, it seems like something like this happens every couple of years...
1995 - Cessna hits white house
2001 - 9/11
2002 - Cessna hits capital one building in Tampa