Afghan and U.S. officials says a U.S. service member walked off his base early Sunday in southern Afghanistan and began shooting Afghan civilians.

NATO says it has detained the service member and is investigating the incident in southern Kandahar province.

A NATO spokesman has confirmed “multiple” people were wounded in the attack. He has not confirmed Afghan reports that several people were killed in the assault.

The U.S. Embassy in Afghanistan said Sunday (in a statement) the person responsible for the attack will be “brought to justice.”

NATO says the shooting is “deeply regrettable” and more information well be released “as appropriate.”

There was no word on what might have motivated the service member's actions.

The shooting comes after weeks of tense relations between U.S. forces and their Afghan hosts, following the burning of Qurans at a U.S. military base. Though U.S. officials apologized and said the burning was an accident, the incident sparked violent protests and attacks across the country, killing dozens of people. There has also been a series of attacks by Afghan soldiers against foreign troops.