Sales are up at some gun stores after the mass shooting in Las Vegas. But does being armed make you safer? The NRA says crime is less likely around armed citizens. Critics say more guns means more gun violence. So are gun owners buying a reliable means of defense — or a false sense of security? Joining us to discuss it are John Donohue, a law professor at Stanford, Kris Brown, co-president of the Brady Campaign to Prevent Gun Violence, John Lott, president of the Crime Prevention Research Center, Porochista Khakpour, author of "Why Did Nancy Lanza Love Guns?" for Slate and Suzanna Hupp, author of the book "From Luby's to the Legislature: One Women's Fight Against Gun Control."