When Trip has found the bag, he opens it to find out what is inside. A few moments later, when he tries to run from the angry mob, the bag is still open. In the next shot, running towards the high fence, the bag is closed. It would have been impossible for him to close the bag while running.
For a significant portion of the film Trip carries a jerry can of fuel for the stricken truck. The way he carries the container and the way it moves, it is obviously empty.