While it may be days before it becomes clear who fired on whom first, the incident illustrates how tense relations have become between international troops and their Afghan allies.
Officials on both sides went into damage control mode, arguing that Saturday's violence did not mark a new low in Afghan-U.S. relations and urging patience while investigators tried to figure out exactly what had happened.
The deputy commander of NATO's military force in Afghanistan, British Lt. Gen. Adrian Bradshaw, called a last-minute news conference in Kabul to address the incident, even though he had few details to give.
He said the initial report of an insider attack should be amended to note that the incident "is now understood possibly to have involved insurgent fire," and tried to stress that relations between international troops and their Afghan allies "are very strong and very effective."
A spokesman for the Afghan Defense Ministry, Gen. Zahir Azimi, also sought to downplay the incident.
"In a misunderstanding shooting broke out between Afghan army and ISAF forces. As a result of the shooting, three army soldiers were killed, three other soldiers were wounded and number of ISAF forces were killed and wounded," Azimi said in a statement.
One U.S. official confirmed that the service member killed was American, while another confirmed that the civilian was also American. The officials spoke on condition of anonymity because the nationality of the dead had not yet been formally announced.
The number of American military dead reflects an Associated Press count of those members of the armed services killed inside Afghanistan since the U.S.-led invasion on Oct. 7, 2001.
In the south meanwhile, three Afghan police officers were killed when insurgents attacked a checkpoint in Helmand province Sunday morning, provincial police spokesman Fareed Ahmad said.