A man wearing an Afghan police uniform shot and killed three U.S. Special Forces troops Thursday night as they met with tribal leaders in southern Afghanistan, Afghan and U.S. officials said. It was the 25th incident this year in which Afghan soldiers or police officers turned their weapons on NATO troops with fatal consequences.

Thursday’s incident, the third such attack this week, was particularly devastating because of its scale and the elite troops who were targeted. U.S. Special Forces are scattered across the country to carry out “village stability operations” — a responsibility that often entails training local police officers, many of whom once had ties to the Taliban, and navigating fierce tribal rivalries.

The three service members were shot by a single assailant as they prepared to dine with tribal leaders at an Afghan checkpoint in the Sangin district of Helmand province, said Sangin Gov. Mohammad Sharif, who identified them as Special Forces troops. The assailant, whom several Afghan officials identified as a police officer named Asadullah, then fled the scene.

Further details of the incident were hazy Friday night, when the bodies of the three Special Forces members arrived at Helmand’s Camp Leatherneck for a traditional “ramp ceremony,” the return of a fallen service member’s remains back home.

Maj. Lori Hodge, a U.S. military spokeswoman, said in a statement only that “three U.S. Forces-
Afghanistan service members died following an attack by an individual wearing an Afghan uniform in southwest Afghanistan today.” Afghan and U.S. officials said the attack was being investigated.

Reached by telephone, Asadullah’s father, Shamsullah Sahraye Alokozai, denied the allegations against his son, saying that he was a loyal police officer who had joined the force four years ago.

“The American forces have given their lives for us. Why would he do this?” he said.

Qari Yousef Ahmadi, a Taliban spokesman, said Asadullah joined the Taliban after fleeing the scene.

As NATO troops leave Afghanistan, the coalition is increasingly relying on small groups of well-trained solders to advise and assist their Afghan counterparts. Members of the U.S. Special Forces maintain particularly close ties with the officers whom they mentor, living in the rural villages where Afghan Local Police were recruited to boost security. Those assignments often bring risks that even Afghan officials sometimes struggle to understand.

“Did the men have to hold their meeting at night?” Sharif said. “It’s a dangerous time.”

On Tuesday, two men in Afghan army uniforms shot and killed a U.S. soldier and injured two others in the eastern province of Paktia. On Wednesday, three NATO troops were killed when two suicide bombers targeted them as they walked to a meeting of Afghan officials in the eastern province of Konar, where the bulk of coalition forces are Americans.

U.S. officials say many of those incidents do not involve Taliban infiltration but are violent responses to interpersonal disputes.