At least seven police were killed when one of their colleagues opened fire on them in the southern Kandahar Province on August 4, officials say.
The Taliban has claimed the attack.
The attack, which occurred in the Tor Kotal area in the Shah Wali Kot district, was the latest of so-called "insider attacks," when an Afghan police officer or soldier turns his weapon on Afghan forces or international troops.
Jamal Naser Barekzai, a provincial spokesman, said the attacker fled the scene of the shooting. Barekzai said an investigation was under way.
Taliban spokesman Qari Yusouf Ahmadi said the attacker, who was their "infiltrator," joined the Taliban.
The Taliban now effectively controls about half the country and carries out near-daily attacks.
Last week, two U.S. soldiers were shot and killed by an Afghan soldier in the same district. The insurgents dubbed the attacker, who is in custody, a "hero."