Your observations in a crowded aquarium are NOT a proper example of natural behavior. Not only do most gar get bigger than bass, they also regularly prey on them in the wild. Aside from the traumatogenic problems they pose, gar also have highly toxic eggs and milt. Any fish that eat the eggs will in turn, become toxic themselves, poisoning lots of birds.
It is far more likely that these are spotted gar, which are far more popular and grow large enough to swallow adult bass.