The attack on Saturday unfolded outside a building in Palmyra where Syrian Interior Ministry officials from the capital, Damascus, were meeting with their counterparts in the city, according to a U.S. official.

The American soldiers and their interpreter were providing security outside when a lone gunman opened fire on them from a nearby building with what appeared to be a machine-gun, the official said. Syrian security forces then opened fire and killed the gunman, according to the American official and Syrian officials.