While I'm not going back to verify where those three SUVs came from, and it's been awhile since I've seen the film, only two additional people are killed after those last three SUVs blow up, and as the other two SUVs seen earlier in the film had full complements of four soldiers a piece, we have every reason to believe that these were full as well. That would account for the last eight bodies. They were apparently just too scared to get out of the car. Not that we blame them.