The general appears to be the highest-ranking officer in the American military to die in hostilities overseas, since the Vietnam War.
Correspondent: Jane Cowan, North America correspondent
Speakers: Rear Admiral John Kirby, Pentagon spokesman; Peter Bergen, national security analyst
JANE COWAN: The two star major general was shot at close range when a gunman dressed in an Afghan army uniform opened fire with what's believed to be a light machine gun.
The attack happened at a British-run military training academy on the outskirts of Kabul.
As many as 15 other NATO soldiers including a German brigadier general were injured in the burst of gunfire.
The Pentagon spokesman rear admiral John Kirby.
JOHN KIRBY: The insider threat, it's a pernicious threat and it's difficult to always ascertain, to come to grips with the scope of it. Anywhere you are, particularly in a place like Afghanistan. Afghanistan is still a warzone.
JANE COWAN: It's the first so called "green on blue" aggression in months, this kind of violence having subsided since 2012 when more than 50 coalition troops were killed in dozens of attacks.
The Afghan soldier, who was shot dead, had apparently gone through a vetting process.
Coming as foreign troops prepare to withdraw from Afghanistan at the end of the year, national security analyst Peter Bergen says the death of such a high level officer can't help but raise questions.
PETER BERGEN: People will take another perhaps sceptical look at the whole question of if we do leave US soldiers behind after the combatants have pulled out in December 2014, if indeed the United States and Afghanistan do sign some kind of basing agreement and there is presence of US troops that would number in the many thousands, many of them will be advised there is, by definition, training facility you're going to be in contact with Afghan soldiers. So it raises a lot of questions about how best to protect coalition troops in that circumstance.
JANE COWAN: While praising the attack, the Taliban isn't claiming responsibility.
Afghan and American commanders have previously attributed most insider attacks to ordinary soldiers alienated by the continued presence of foreign troops, rather than Taliban fighters planted in Afghan army units.
The Pentagon's John Kirby insists one grim day doesn't necessarily change American faith in the Afghan security forces.
JOHN KIRBY: I've seen no indication that there's a degradation of trust between coalition members and their Afghan counterparts. The Afghan national security forces continue to perform at a very strong level of competence, and confidence, and warfare capability.
JANE COWAN: Several Afghan army officers are also said to have been wounded in what the Afghan president Hamid Karzai condemned as a "cowardly act by enemies who don't want to see Afghanistan have strong institutions".