The Afghan National Army soldier opened fired at the British-run training facility in Kabul on Tuesday morning after a dispute broke out, killing the US major-general and wounding up to 15 other personnel, including a German brigadier general and an Afghan general.
The incident took place at the Afghanistan National Military Academy, located at the Marshal Fahim National Defense University in Kabul.
Greene, deputy commander of Combined Security Transition Command-Afghanistan, was the highest-ranking American official killed in Afghanistan since the US-led war began there in October 2001.
According to the Pentagon website, the 55-year-old was deployed to Afghanistan in January 2014.
The shooting was the first so-called “insider attack” or “green-on-blue attack” in several months.
The previous green-on-blue attacks, in which Afghan security forces turn their weapons against foreign forces occupying their country, mostly took place in 2012. The attacks left at least 53 foreign troops dead.
“Today’s tragic incident is a painful reminder that our servicemen and women are still serving and sacrificing in Afghanistan,” White House press secretary Josh Earnest said on Tuesday.
Afghanistan’s Ministry of Defense said the Afghan soldier who opened fire was shot dead. Afghan defense ministry sources told a British broadcaster that the soldier was recruited three years ago.
According to Pentagon officials, Greene was believed to be the first US general killed in an overseas war since the Vietnam War.
The United States and its allies invaded Afghanistan on October 7, 2001 as part of Washington’s so-called war on terror. The offensive removed the Taliban from power, but insecurity continues to rise across the country, despite the presence of thousands of US-led troops.