Cameron calls security emergency after brutal killing on London street
Official sources say assailants shouted 'Allahu Akbar' and tried to film attack

One person was killed and at least two people were wounded in a violent attack near a military barracks in London, British officials said yesterday.
Prime Minister David Cameron called an emergency security meeting in response.
Scotland Yard said police officers responded to reports of the assault yesterday afternoon in the London neighbourhood of Woolwich, just a few blocks from a military training barracks. London Ambulance Service said a man was found dead at the scene and two others were taken to hospitals, one in serious condition.
Britain's Ministry of Defence said it was urgently investigating reports that a serving soldier was involved in the incident.
The BBC's website quoted senior Whitehall sources as saying the Woolwich suspects are thought to have tried to film their attack while shouting Allahu akbar (God is great).