Octavius is an asshole. He feels the mitary is the greatest thing since underwear, and is determined to prove it. So determined he will shoot at anything. He believes that the autobots are invading pests that must be destroyed, or bend to the will of the military. They won't, thus they must die. He fails though, as his pride makes him arrogant. Thus, because he feels he can't be defeated, he is easily destroyed.