Originally Posted by GalaxyRed13
Should point out that the video here does not work. I finished a convoy with just using my fists, and the achievement didn't unlock for me. It wasn't that convoy, though, but another one on the map. I doubt which convoy makes any difference.
Were the people on the ground still moving a bit? If they weren't then they died. Can sometimes happen that the guards shoot & kill each other, or that you accidentally stomp an unconcious person (which will kill them as well). Could also be a bug - there are quite many in this game.
Everything is alright with the vid and you just need to use your fists instead of lethal weapons. This has been confirmed multiple times.