The attack caught the US military by surprise. General officers are rarely in situations where they face attack, and even more rarely wounded.
Among those present during the attack was Army General Austin "Scott" Miller, the top US officer in Afghanistan. Butler has said that the US officials present were caught in the crossfire after a gunman started shooting. The Taliban claimed the attack and said Miller was among the main targets.
Smiley has served in the Army for just over 30 years and became a general in May 2017, according to an official biography.
He deployed in Afghanistan this northern summer, taking command of a unit with headquarters in Kandahar known as Train, Advise, Assist and Command-South. The headquarters largely comprises members of the 40th Infantry Division, a unit of the California Army National Guard. Smiley has commanded guard units in California for years.
The Afghan officials killed include Kandahar's top police general, Abdul Raziq, a powerful but controversial security official who had survived numerous assassination attempts. He had risen to power while clearing the Taliban from Kandahar but was accused of extrajudicial killings, torture and other human rights abuses. He denied the allegations.
Also killed was Kandahar's intelligence chief, Abdul Momin. The Governor, Zalmai Wessa, was shot but survived.
The attack prompted the Afghan Government to postpone voting in Kandahar for parliamentary elections by a week. The elections were held at the weekend across most of the country, with some Afghans waiting hours to vote.
"Today we proved together that we uphold democracy," President Ashraf Ghani tweeted. "With casting our ballots without fear we honour the sacrifices of the fallen."