The police officer was shot and killed immediately after killing the American troops, CBS News reported. An official NATO investigation is underway.
According to the Associated Press, The shooter had been recruited by the Afghan Local Police just five days ago. The Afghan Local Police is a network of regional militias backed by the international military alliance and is largely trained by NATO forces.
The attack is the latest in a series of "green-on-blue" attacks by members of the Afghan security forces.
BBC News reports that about 130,000 ("blue") coalition troops are fighting insurgents alongside 350,000 ("green") Afghans. But there is mounting concern over attacks on Nato troops by their Afghan allies.
Earlier this week Voice of America reported that US Ambassador to Afghanistan James Cunningham told reporters that the United States will work very closely with Afghan authorities to prevent these “painful” incidents from happening in the future.
Attacks by international troops have escalated this year; at least 36 foreign troops have been killed by Afghan service members, AP reported.
CBS News reported that the US military, working with Afghan commanders, has implemented an eight-point vetting process to try and identify and exclude Afghan recruits who pose a threat. Neither US Defense Secretary Leon Panetta, nor other US commanders have elaborated on any new steps to confront the problem.
Meanwhile, Afghan Taliban leader Mullah Mohammad Omar urged insurgent fighters to avoid civilian deaths after 63 people were killed in Afghanistan after a series of suicide bombings.
Omar, who was speaking to the Afghan people ahead of the Eid-al-Fitr festival that follows the holy month of Ramadan, said that the Taliban had successfully infiltrated Afghan security forces, but would "employ tactics that do not cause harm to life and property of the common countrymen".