McKenzie said the decision to order the airstrike "was a mistake" and took full responsibility for the "tragic outcome" of the attack.
"Having thoroughly reviewed the findings of the investigation and the supporting analysis by inter-agency partners, I am now convinced that as many as 10 civilians, including up to seven children, were tragically killed in that strike," the US general added.
"Moreover, we now assess that it is unlikely that the vehicle and those who died were associated with ISIS-K [Daesh] or were a direct threat to US forces," he added. "I offer my profound condolences to the family and friends of those who were killed ... It was a mistake and I offer my sincere apology."
The airstrike was ordered in the aftermath of a string of deadly terrorist attacks by Daesh-Khorasan that targeted crowds of civilians as well as US and Taliban* soldiers outside Hamid Karzai International Airport on August 26. The bombings killed nearly 200 people and injured thousands.
One airstrike on August 28 in Nangarhar Province east of Kabul was purported to have killed two Daesh commanders responsible for orchestrating the attacks. A second strike on August 29 hit a vehicle in Kabul that CENTCOM claimed was carrying a car bomb intended to be imminently used in a terrorist attack.
Bill Urban, a CENTCOM spokesperson, claimed at the time that the airstrike caused "significant secondary explosions" by setting off the car bomb, and that the strike had killed multiple Daesh fighters and no civilians. However, it soon became clear that at least 10 civilians had been killed, including seven children.
The driver of the car, Zemari Ahmadi, was an employee of the US non-governmental organization (NGO) Nutrition and Education International. He was most likely on a trip to refill water containers for his home. All 10 people killed were member of his family, the youngest of whom was 2 years old.
McKenzie added on Friday that the US was exploring the idea of making restitution payments to the victims of the drone strike.
Pentagon press secretary John Kirby also said on Friday that Defense Secretary Lloyd Austin had asked for a "thorough review" of the drone strike investigation, which would include accountability.
*Taliban, Daesh: terrorist groups outlawed in many countries