The shooter, who served as the Governor's bodyguard, was also killed in the incident.
The Americans were wounded in the cross-fire after gunfire erupted at the palace, Peters said.
In an interview with AFP a year ago, Raziq said the Taliban had targeted him "countless times", adding he could remember 20 of the incidents, including at least eight suicide attacks. The U.S. military released a statement confirming that Miller, who was in the compound at the time of the attack, was not hurt, but that three Americans had been wounded.
The Taliban claimed responsibility for the October 18 assault that came just two days before parliamentary elections.
Miller, 57, took over last month as the top USA commander in Afghanistan, replacing Gen. John W. Nicholson Jr.
Three top Afghan officials and a local journalist were killed in a shooting at a meeting attended by Afghan and USA officials in this southern Afghan province of Kandahar on Thursday.
The attack on the North Atlantic Treaty Organisation convoy came at the end of a particularly violent day across Afghanistan as tensions are rising ahead of the country's parliamentary elections on Saturday.
Raziq had been police chief of Kandahar since 2011 and had been accused of severe human rights abuses, including running a secret torture center.
"At 3:30 p.m., after a meeting about the security of elections, when the high-ranking participants were heading to helicopters, an enemy infiltrator opened fire on them", the deputy minister of interior, Gen. Akhtar Mohammad Ibrahimi, said at a news conference.
Afghan security forces cordoned off the area as a U.S. military helicopter circled overhead.
However, the USA military said the attack would have no effect on its military presence aimed at bringing the Taliban to the negotiating table: "This attack will not change U.S. resolve in our South Asia strategy", Defense Department spokesman Lieutenant Colonel Kone Faulkner said. North Atlantic Treaty Organisation troops, which handed over security to Afghan forces at the end of 2014, mostly train and assist with air power.
Mattis called the death of Gen. Raziq a "tragic loss of a patriot".
"He was seen as crucial to the security of Kandahar, the birthplace of the Taliban where the group continued to have a presence".
The U.N. Security Council condemned the attacks and others recently in Afghanistan and said violence or threats meant to disrupt the elections were unacceptable.
"This serious attack seems likely to shake the confidence of the government as security forces prepare for one of their largest operations of the year, guarding more than 5000 polling centres in the upcoming parliamentary elections", said Graeme Smith, a consultant for the conflict monitoring organisation International Crisis Group.
Several current and former officials confirmed the death of Abdul Raziq, 39, a close US ally and fierce anti-Taliban fighter.
At least 10 candidates have been killed so far, including Abdul Jabar Qahraman who was blown up Wednesday by a bomb placed under his sofa in the southern province of Helmand.