But the local commander of the NDS intelligence service and the Kandahar provincial governor Zalmay Wesa were also killed.
U.S. Defense Secretary Jim Mattis said the killing of the Kandahar police chief is unlikely to fundamentally weaken the security situation.
"Initial reports indicate this was an Afghan-on-Afghan incident", Peters said.
A Taliban spokesman who claimed responsibility for the attack tells The Associated Press that Miller, was the target.
Mr. Mattis, who had known General Abdul Razeq, the police commander in southern Kandahar, on Friday described his death as "the loss of a patriot".
He had been a key figure in the United States strategy of securing the southern region against the Taliban.
Three senior Afghan officials were reported to be among the casualties, but there were conflicting accounts on whether they were killed or wounded.
Abdul Raziq, a lieutenant general in the Afghan National Police, was a controversial official who had been repeatedly accused of torturing detainees and other abuses during his rise to power in Kandahar.
According to sources, at least one of the governor's bodyguards opened fire on the officials.
Security was stepped up in Kandahar, with buildings around the governor's office sealed off ahead of Friday's expected arrival of a team of investigators from Kabul, the capital.
But he predicted that the brazen attack would not have a long-term impact on security in Kandahar, one of Afghanistan's most strategically important and contested provinces in America's longest war.
He had survived a number of assassination attempts, including suicide attacks, but had managed to strengthen security in Kandahar, the birthplace of the Taliban militants.
Raziq narrowly escaped an attack past year in which five diplomats from the United Arab Emirates were killed in Kandahar.
Taliban spokesman Zabihullah Mujahid said the Doha discussion was "about ending occupation and working towards finding a peaceful resolution to the Afghan conflict".
It was unclear if the attack would affect the process, following a meeting last week of Taliban officials and the US special envoy, Zalmay Khalilzad, but complicates an already hard situation.
Security has been steadily deteriorating in Afghanistan with increasingly brazen attacks being carried out by insurgents and Afghanistan's security forces have been on high alert ahead of Saturday's elections.
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.