Two American military service members were killed by an Afghan soldier in an apparent “insider attack” Wednesday at a military base in southwestern Afghanistan — according to U.S. officials.

The Afghan Helmand provincial chief, Mohammad Karim Attal, said he believes that both of the troops killed were coalition soldiers from the U.S. training Afghan forces at Camp Bastion, right in the middle of the Helmand province.

An official from the Pentagon has also confirmed that the two troops killed were indeed American.

More from the Washington Post:

In Helmand, Taliban insurgents captured the province’s Musa Qala district after a heavy clash with Afghan government forces, local officials said. They said 25 members of the security forces were killed in the fighting in the northern part of the province.

The attack on the foreign troops, members of a U.S.-led coalition in Afghanistan, was carried out by one person in an Afghan army uniform who opened fire on a vehicle on an Afghan base in Helmand, the coalition said in a statement.

In addition, the coalition statement also said that other service members among the two slain troops returned fire on the assailant and “another individual wearing an Afghan army uniform”.

Stay tuned to this blog for updates on this still developing story.