Maybe Obama was crying because he realized that criminals are the ones doing the crimes, and criminals break laws, so whatever new laws he creates concerning gun control will do nothing to stop such heinous events. Or maybe he was crying because he learned that since Chicago passed a law allowing private citizens to carry guns, the crime rate has dropped in that city. As Illinois State Rifle Association's executive director, Richard Pearson, explained, “It isn’t any coincidence crime rates started to go down when concealed carry was permitted. Just the idea that the criminals don’t know who’s armed and who isn’t has a deterrence effect.”
Or maybe it was just that fact that he's only got one year left to fly around the world in Air Force One and have big parties at the White House and hobnob with celebrities that's got him down.