The shooting took place in a building and while I haven't seen it or any photos, I know it is multistoried because a number of Afghan Army/ Police types injured themselves bailing out of the second floor rather than figure out what all of that shooting nonsense was about....
If he was in an area populated by US personnel who are training/ mentoring the Afghan Air Force, I can easily (sadly) see how you could get the drop on 8-10 quite easily. I won't go into all of the details why I believe this to be easy, but if you're dealing with aircrew in a tight environment like a briefing room or conference room, aircrew who 1) Don't see the guy as a threat. 2) Never expect to draw their weapons which is reflected in some of the ridiculous shoulder holsters I see around BAF 3) Barely fire at all each year beyond annual qualifications and 4) Would have to chamber a round before they can use their weapons anyway?
Under that scenario I can easily see 8-10 killed in a short amount of time. The shooting starts, the guy gets maybe 2 or 3 before anyone can process what is going on. A panic ensues, folks start ripping and clawing at their jacked up, floppy, untied shoulder holsters or trying to peel back the velcro on an old style Bianchi or maybe they have a Serpa and simply don't practice the draw (some of the belts around here are straight out of Tombstone and while they may look cool and feel comfortable, good luck drawing from one)...now panic really ratchets up as no one is returning fire. In a confined space (if this is the case) there's no place to hide so 2 maybe 3 more go down. Some finally draw their weapons and reflexively pull the trigger on an empty chamber, now they have to chamber a round....
In a room full of people who aren't thinking or training for combat, I can see it.
Please note that all of the above is pure speculation based on the CNN article. Replace "airmen" with "soldiers" (read: fobbits) and I can easily see the same outcome.