After I saw the first video, I did some googling around and reading about the rules of engagement during an insurgency. Under the Geneva Convention, clearly identified medical personnel treating combatants removed from combat are protected. However, if an armed combatant is attempting to help another combatant get to cover, they're both fair game. There's a grey area when it's not clear if a person helping a combatan…
Everyone picking up the bodies and from the van was clearly UNARMED. Unarmed non-combatants were picking up the body of an unarmed non-combatant who never held a weapon.
In the moment of the firefight it was unclear whether the van was armed or not. Was was clear to the soldiers was that the van responded very quickly to a group of wounded people who had several confirmed weapons among them. Also, as others have mentioned, the soldiers knew the insurgency has used similar tactics in the past to salvage weapons and ammo.