The Hero Inkopolis Deterred

Agent 4 is a rare breed of a creature. Being half firefly Inkling and half mimic Octarian can have its perks, but it certainly has it's downsides- especially when you're still learning to control it. But after the many reports of Agent 4's death, followed by sightings shortly thereafter, many believe that Agent 4 is a ghost or some other powerful being. So the question remains... who is this vigilante? And what motivates them?