I don't think anyone is thinking concussions are the most likely reason, but given how much the story has been in the press lately, I'm not surprised people are bringing it up as a possibility. There could be a million reasons why but in the last 2 years Dave Duerson and Junior Seau both killed themselves and (I believe) their suicides were traced back to concussion related injuries (I apologize if this is incorrect). Also within the last decade in a different realm of entertainment, Chris Benoit snapped and killed his wife, young kids, and later himself, and afterwords was shown to have major brain damage caused by concussions. It's something that's fresh in the minds of your average football/sports fan. I think its just so random and out of place when a NFL starting linebacker randomly decides to murder his girlfriend in front of her mother and then drives to his team's practice facility to kill himself in front of his bosses, people immediately try to make sense of a senseless situation.