Semi-automatic rifles are seen for sale in a gun shop in Las Vegas, Nevada on October 4, 2017. Mass killer Stephen Paddock used semi-automatic weapons which he modified with "bump-fire stock" to make them fire at the same speed as a fully automatic weapon when he killed 58 people and injured over 500 in the worst mass shooting in modern American history on October 1, 2017 at a country music festival in Las Vegas. / AFP PHOTO / Robyn Beck