KABUL, Afghanistan (AP) — Afghan President Hamid Karzai lashed out at the United States on Friday, saying he is at the “end of the rope” because of the lack of U.S. cooperation into a probe of a killing spree allegedly carried out by an American soldier.

In a meeting with families of the 16 Afghan civilians killed Sunday in southern Afghanistan, Karzai said the delegation he sent to investigate the shootings did not receive the cooperation the Afghans expected from American officials.

During the meeting, the relatives of the dead insisted there must have been more than one shooter and argued that they did not receive all the information they asked for from Americans.