Is it possible that K and B came up on the van of L and C not realizing anyone was inside? They were maybe wanting to loot it or use it for target practice? Then were surprised when Lucas and Chynna came out?
There seems to have been quite the escalation in violence from the L and C crime scene to the LD one, in the sense that, from what the coroner’s report indicates, L and C were shot multiple times whereas there was blunt force trauma and burn marks on LD. Plus the fact that LD’s family have requested his cause of death not be released. The multiple shots fired at L and C makes me think K and B were stunned when two people emerged from the van, so just started shooting them. Their subsequent trip to the Yukon gave them time to discuss what had happened and create a plan for the next encounter. I believe K and B were taken by surprise by having to face two targets as they seemed to enjoy the idea of a 2 against one situation better. Hence, the encounter with the one man in Haines Junction and then LD. MOO.
I also believe we will discover more about KM’s background over time. I find it hard to believe there were no signs that he had issues leading up to this horrendous event.