Is it the one where a science experiment goes wrong and a surge of (some sort of ) energy is released every so often with the surge happening quicker and quicker each.
Each time a surge happens only those that die at that precise moment are actually alive.
The hero figures out what happened and tries to stop the last devistating surge by ramming it with a truck or something and ends up dead when it happens and is therefore that last surviving human on a distant planet not knowing if his attempt were successful or not?