An Afghan policewoman has killed a US civilian aide at the police headquarters in Kabul.
It is believed to be the first such insider killing carried out by a woman. She is now in custody.
Earlier in a separate incident on Monday, at least five policemen were killed by another officer in northern Afghanistan. The man escaped, taking the weapons of his colleagues with him.
In Kabul, officials said the female officer, who they named only as Nargis, 33, arrived at police headquarters looking for the police chief, the governor of Kabul or the head of the criminal investigation department.
When she was unable to locate them, she went to a canteen and fired one bullet at the aide. She then fired at officers who tried to arrest her.
Afghan officials said the woman was married to an officer with the criminal investigation department and has three children.
She graduated from the national police academy six years ago with the rank of sergeant.
Investigators are checking whether she has links to the Taliban or al-Qaeda.
More than 50 members of the NATO force in Afghanistan have been killed by Afghans wearing army or police uniforms this year.
Some of the attacks were carried out by Taliban infiltrators, others by Afghans angry at the actions of their foreign colleagues. Often the precise motive is unclear.