A friendly reception turns deadly in Afghanistan, an US general has been killed by gun fire. The fallout from Americans higher serenky causality seems be a none more. Let's get started.       

Major general H. shot dead by an Afghan soldier who badly wounded many more. Jim Sciutto has been working on the sources, joins us now from Washington.

So, what are we now learning about how this all happen, Jim?

"Anderson, this took place in part of routine visit to Afghanistan's national defense university. This is where Afghanistan coalition forces, including US forces train Afghan military leaders and officers. Arguably the Afghan west point. Several senior officers involving, including General Green as well as a German general who was injured as well in this attack, as well as 8 other Americans. A total of 15 injured. And I'm told the solider the Afghan solider who turned his weapon on these Americans and coalition officers had been with him unit for some time. In fact, he's been va. He'd gone through a very serious vet process that they have for Afghan soldiers to prevent attacks just like this one, so called green on blue attacks and seeing how he got through that vetting process and still carrying out his attacks is going to be one of the major focuses of the investigation of which is now underway.

And an officer no less. The Taliban had acknowledged the killing but they have not claimed credit for it. Right?   

They have not, no. Doesn't mean that won't change but at this point, they haven't claimed credit. So, the open question now is what caused this Afghan solider to turn? Was it a personal grievance? Was it his own affinity for the Taliban? We don't know yet and that's another subject to the military investigation.     

What do we know the general who lost his life in the attack?

So, General Green, a 34-year veteran in the military. He was the deputy commander of what's called the combined security transition command. This is a command whose job it was to help transition from coalition security controller in Afghanistan to Afghan security control as coalition forces, including American withdraw. So, you know, this presents a real problem going forward because it presents an open question: What does this say about a readiness of Afghan forces to take on this attack. Now, to be fair, attacks like this have decreased remarkably since 2012. General Green gives his life. Part of the military family. His wife was a retired military colonel as well and notification just going out to the family today. So sad moment for that family, no question. But of course, the other 8 Americans injured. I'm told some of them seriously.                          

Yeah, for a lot of families tonight. Jim Sciutto, appreciate the update.

There are some 30000 American troops still in Afghanistan and it's far from the first time they face this kind of sneak attack as Jim mentioned. At their peak in 2012, accodring to the foundation for defense of democracies, they accounted for 15% of all coalition fatalities. It's an ugly facts that many wars and a prominent part particular of the war in Afghanistan. We dig deeper now with CIA and FBI counter charge veteran, P. Also, military analyst, a retired air force lieutenant colonel Rick F.

Colonel F., I mean this is clearly a vetting problem here and I mean, this was an officer in Afghan military, so that raises all sort of problems but talk about the vetting process, I mean, it's supposedly extensive, but is it really?       

Well, it has change since 2012 because we have that rash of killings in 2012. We approached Afghan and said you've got to your vetting so we have less of these incidents. So, the institute of the process, they actually brought in some computers and they are matching their database with ours now. But it's not quiet there yet as we have seen. And Jim is right. The incidents are down but the vetting process is totally an Afghan issue right now. And then we're given that result and there is not much we can do about this as we withdraw the....   

...control the vetting.

Yes, they do, they do. And so we have to take their word for it once its people are vetted. We can get the result and run it through our computer but they're the one who actually do all the investigation.