 President Samir Hassan says an attacker wielding an assault rifle has been shot dead after killing three police officers and an employee of a private security company near the French embassy in the Tanzanian commercial capital Dar es Salaam. Reacting on Twitter, Hassan said the attacker had been neutralized and calm has returned. Inspector General of Police Simon Siro said police were trying to identify the attacker in a short video published by Millard Ayo at Tanzanian news website. He said the gunman's motives remained unknown.