A man dressed all in black pulls a gun from his bag and shoots three people in seconds. Then the narrator's voice comes over the video: "Your survival may depend on whether you have a plan." This is a $200,000 training video that has been developed to help people survive what the US calls an 'active shooter event'. It's the city of Houston's answer to the problem in a country where gun sales are up 20 per cent on last year and there is less support than ever before for stricter gun laws. "Most of the time I carry this Springfield XD nine millimetre. It's a smaller firearm," Sharon says. She's an ordinary housewife, but she represents an increasing number of Americans who feel guns provide safety and not a threat. So as gun laws seem likely to remain the same, it falls to the police to provide instructions on how to survive attacks. "The goal is not just to nurse the problem, but to actually solve it," officer Chris Paine tells us. Though on past record it seems unlikely the number of shootings in the US is going to decrease any time soon.