A fatal mass shooting in the cloistered environs of Prague might seem a bolt from the blue. In a city historically renowned for defenestrations but less for violent crime, safety and security are taken for granted much more than in most European capitals. The reaction of Prague’s mayor, Bohuslav Svoboda, whose offices at Prague New Town Hall lie a short distance from the scene of the crime, conveyed many locals’ bewilderment as they struggled to digest the horror that had unfolded. “We always thought that this was a thing that did not concern us,” he told Ceske Televize, the national...