Sorry, I have been a bit busy, but my complete recount:
We were clearing out the NWAF, as stated, and we moved up along the east side. I stayed back and got on the radio, climbing up the large industrial building at the North Eastern side, keeping a lookout for people. To be honest, I didn't even see where their group came from when our group was in the tent city area, but when I looked down and saw them all, I radio'd and asked if they needed help, to which, I got no response, but I heard @ThePizzaMan and @Outlawe over the radio. I called in for Frenchy (who also wasn't there for the entirety), and I had a shotgun so I figured if something happened I ought to be down there, so I climbed down and moved towards them. I reached the H-barriers at the edge of tent city and heard a barrage of gunshots. I ran in pretty much at the end, with about 5-6 dead bodies and just me and @Outlawe left. I dropped my shotgun, grabbed an AK and an M4 (the AK was deleted by the admin after the event), and then Frenchy arrived. The three of us then left the airfield after securing all the loot we could.
As far as I recall, @Outlawe was telling our group to ask them questions, find out who they are, see if they know anything about the groups in the area that have been causing trouble for people. After what I gathered was pretty docile conversation @ThePizzaMan told them, which I heard over the radio as I was moving over, to set their radios down. I didn't hear the reply, but he said again, [Aussie accent]: 'Drop your radios on the ground for us', once more there was no reply, and finally he said "Lads drop the radios right now", and that's when the gunfire began.
Two things that I found interesting enough to note, the conversation was pretty normal. There weren't any hostilities from our group or demands until @ThePizzaMan told them to drop their radios, and at the first moment of a demand, the other party immediately opened fire. The second, which I don't honestly know if it was them, was that people were very obviously loot cycling the area, and the server wasn't up past a restart very long. From the point that @ThePizzaMan told them to drop the radios to the point where the three of them (Larsons + Dunning) were gunned down, there were mere seconds, so it was quite obvious they had no reply or intention of replying, and opted to just try and kill them.