(Official White House Photo by Pete Souza)

President Obama called Afghan President Hamid Karzai today to express his sympathy in the shooting deaths of at least 16 civilians southwest of Kandahar. A United States service member is accused of the killings.

In a written statement, Obama called the incident "shocking" and sought to reassure it was not a representation of the American military.

"I offer my condolences to the families and loved ones of those who lost their lives, and to the people of Afghanistan, who have endured too much violence and suffering," he said.

He said his administration is still gathering facts on the incident and will hold whoever is responsible fully accountable. The language is tougher and broader than previous statements on the situation and could signal the administration would take action against military commanders who failed to sense the trouble.

Aides say the president was briefed on the shootings this morning before his call with Karzai. The conversation took place inside Obama's motorcade as he traveled to his daughter's basketball game, an unusual location for a call of such gravity.

The shootings come in the wake of increasing turmoil in the country, spurred in part by the recent unintentional Koran burnings at a U.S. base. Six U.S. service members have been killed in the weeks since the incident at the hands of their Afghan counterparts in revenge attacks.