A really stupid bug. Probably the server lost track of the position of the first truck and by having them collide it triggered an explosion. There is an even more frustrating possibility if you are on foot, it had happened to me in one of my first missions: in case you collide with someone else it throws you up into the air like thousands of feet above. The only way to reappear is by respawning.
Nonetheless, we had our lesson out of this disaster. You need to take the wounded out of the burning vehicle as soon as possible and treat them for their heavy wounds immediately. Pushing blood is also a priority given they will 99% have injuries all over their bodies. At this point, I am not sure if there is also some "burning" damage applied to the guys that are left behind in the vehicle.
