The person, or rather demon who shot Goober and rebooG down, was Normac's right hand man, Grimo, a former inkperial hitman in his former life, before being killed by Hakai and Rizu. But his sheer determination to kill them was caught wind by Normac, and claimed to help Grimo, if he was his right hand man. Though little does the great Grimo know, he was lied to. Normac won't kill anybody who isn't supposed to be dead. His pure rage blinded him from Normac's deception. Grimo couldn't even be bothered to question it, all he saw was big powerful man in charge. So he's been doing Normac's dirty work.
Grimo would fly by in a helicopter and jump out and pelt Goober with a Grenade launcher. Goober would cover his face, accepting his fate, but would open his eyes to see Potato, wielding a sword and shield, deflecting the grenades back at Grimo.
Goober: Potato?! You're still alive even after the waffle guy?!
Potato: I don't die that easily.
Goober would toss Potato up to the helicopter, and Potato would kick Grimo out the other side, and before coming down, Potato would jab his sword into the copter's blades, destroying them, making the helicopter come crashing it into an apartment.