The Newtown massacre, in which 20 primary schoolchildren died, has been hailed as a turning point on gun control in America. President Obama wants to ban assault weapons, but his opponents say more guns are the answer, not fewer. At a gun range, Panorama meets the teachers who want to take guns into their classrooms to protect their pupils. With many of America's mass killers having both mental health issues and easy access to guns, Panorama reveals the national crisis in mental healthcare which has left 4.5 million severely mentally ill Americans untreated. And reporter Hilary Andersson goes undercover to show how easy it is in Texas to buy the type of assault weapon used at Newtown, even if you are mentally unstable. Will Newtown finally change things, or will the mass killings continue?