Europe has seen this nightmare before. On 21 August 2015, a gunman armed with an AK-47-style assault rifle, a pistol and a knife opened fire on a Thalys train travelling from Amsterdam to Paris, wounding three passengers before being overpowered near Arras. The attacker, Ayoub El Khazzani, a 25-year-old Moroccan who had trained with Islamist
