An investigation officer of the US Embassy to Yemen was killed on Thursday by masked gunmen on his way to work, a Yemeni security source announced. The shooting was carried out by a gunman on the back of a motor cycle in western Sanaa as the employee, Qassem Aqlan, traveled to the embassy east of the capital. The attackers immediately fled the scene, the source added. Aqlan had worked for the US Embassy for almost 20 years and had been in charge of investigating the embassy intrusion which took place mid-September 2012 by protesters against the anti-Islam film.