The British military forces, based here in Helmand, the neighbouring province to Kandahar, have been working hard to develop a bond of trust with people here but it's delicate work and easily derailed by incidents like this.
They can only hope there are no more serious consequences. In bases across the country they are bracing themselves for difficult days ahead.
The international military strategy in Afghanistan must not be derailed by the massacre of civilians by a US solider, leaders said.
With popular support for the war in Afghanistan fading, President Obama will be hoping for a quiet close to combat operations in 2014.
At least 16 civilians, including nine children, have been killed in an apparent shooting spree by an American soldier in Afghanistan.