With mass shootings an increasing concern in the US and Canada, and many European countries alert to the deadly potential of attacks by armed terrorists, the response to such events by both police and those targeted can be crucial in saving lives; Vernon White, former Chief of Police for Ottawa Police Service, and Joe Carlebach, former Hammersmith and Fulham councillor, explore the approaches used in the police response to active shooters, and what facilities and organisations can be doing to protect their communities.