A police officer who was stabbed by a knifeman in the German city of Mannheim on Friday has died, authorities have confirmed. The attack, in the city’s Marktplatz square, saw a 25-year-old knife-wielding man severely injure six individuals in a shocking attack which was captured on a YouTube live stream. The assailant was caught on video attacking workers outside a campaign tent for German anti-Islamist campaign group Citizens’ Movement Pax Europa (BPE) at 11.30am local time on Friday morning. The live-streamed footage was uploaded by 59-year-old hard-right German activist Michael Stürzenberge…