There is a reason gator gar are always reccomeneded to be kept alone or with other gator gars, they are apex predetors. which means they are high if not the highest fish on the feeding chain natively. For whatever reason he's figured out he's got teeth... and they work. i woulnd't say it's inaccurate to say the fish may have been "annoyed" is anthromorphic.. I've seen cichlids intentionally harass other fish.. from what I understand of PBass this is entirely plausable and the bass being territorial or ignoreing the gars displays could easily have resulted in the ensueing problem. which would explain how all of a sudden the gar is trying to eat it's tank-mates... I will disagree that they are "insane" just apex predetors.
Most incompatablity in fishtanks is due to ignorance of the animals natural behaviors.