Pretty much dumb luck that they gunned this guy down before he hit anyone, which is why this isn't in the headlines. Perhaps blowback from Yemen's embroilment in the joint US-Ethiopia proxy war in Somalia? From SomaliNet, Dec. 6:

A gunman opened fire outside the U.S. Embassy early Tuesday, but was shot by Yemeni security guards and arrested before anyone else was wounded, an Interior Ministry official reported.

The gunman, who was armed with an assault rifle, seemed to be acting alone and he did not breach the security around the embassy, the official said. The gunman was being questioned at a hospital, the official added. Yemen immediately increased security outside the embassy.

Many embassies in the capital, San'a, went on alert this week after they received information that an unspecified terrorist attack was imminent, Yemeni security officials said.

The Yemeni government supports the U.S. campaign against international terrorism and has received U.S. military aid. But its crackdown on militants has suffered a number of reverses, such as the February prison breakout of 23 convicts, some of whom had been jailed for al-Qaida-linked crimes.

See our last post on Yemen.