Bub was apparently in one branch of the United States Military before the Zombie outbreak, possibly the US Army or Marine Infantry seeing as he recognizes ranks and can handle firearms with ease. When the undead apocalypse occurred, Bub died and reanimated. He was one of the zombie specimens captured by the Seminole Storage Facility from the zombie-infested caves.
Rather than dissect Bub like the other zombie specimens, Logan instead tried to successfully domesticate him. He demonstrated this to Sarah and Rhodes by giving Bub several objects which the latter recognized from when he was alive, and remembered .
Eventually, Logan rewards Bub by feeding him the fresh remains of Miller and Johnson. Later, Bub is able to figure out how to remove his chain, and discovered Logan dead in the freezer where he eagerly tried to show the slain man that he removed the chain only to realize he has been killed. Enraged at his mentor's death, Bub acquired a discarded gun and went on a hunt for Rhodes in the complex, attacking Steel before meeting his final objective.
Bub stalked Rhodes through the complex, shooting him several times, until Rhodes bumped into a horde of zombies. Bub shot him once more, causing him to be overwhelmed by the horde. Bub then gave Rhodes a mocking salute before leaving the captain to be torn apart and devoured.
Life as zombie
Nothing is known about Bub before he became a Zombie, but as the movie focuses on him, there's more to him. Bub was first seen in Dr. Mathew "Frankenstein" Logan's Lab. When Dr. Sarah Bowman was sent to inform the former of Captain Henry Rhode's meeting, Bub sneaks up on her only to be restrained by a chain leash attached to the wall. He watches curiously when Logan discusses with Sarah what drives the dead to keep moving and his intent to domesticate them as a temporary means to halt their hunger for flesh. He is later seen when Sarah and Dr. Ted Fisher are invited by Logan, to observe his progress. It is there he reveals he named Bub after his father, a rich surgeon. He let Bub "live" because after many failures, Bub was a success so far. At Sarah and Ted's observance, Logan shows Bub a few toys to help him learn. A toothbrush and a shaving razor, which he used before and a book (Salem's Lot by Stephen King), which was part of a new addition to the experiment.
While Bub plays with the razor and tooth brush he throws them away after a while. When he starts reading the book, Logan congratulates him enthusiastically. Ted argues how pointless it is, due to him witnessing the dead do similar things such as trying to drive a car. However Sarah argues, that it's more on the fact that he didn't attack or try to eat Logan during the demonstration. Rhodes and his Private, Walter Steel; interrupts their conversation at first acting hostile towards Bub, but Logan insists that Bub is docile. He invites them all in the room and hands Bub the phone in an attempt to get him to speak. Steel think's its ridiculous and Rhode's just examines the clipboard.
When Bub speaks saying "Hello Aunt Alicia." Rhodes drops the clip board in shock, gaining Bub's attention. Bub, apparently recognizing Rhodes as a soldier, offers a salute to Rhodes, causing Steel to laugh. This prompts Logan to believe that Bub was in the military in life. Logan asks Rhodes to return the Salute, which he refuses, seeming to anger Bub. As part of a demonstration, Logan asks Sarah to empty her pistol and hand it to Logan. As a show of respect, Logan then salutes Bub before placing the pistol on the table. Bub looks at the pistol and cocks it, aiming at Rhodes, prompting Rhodes to pull his own loaded gun on him. Bub tries to fire his gun, only to hear the pistol click, reacting in fear that the gun is empty. He puts the gun back down, but Rhodes refuses to lower his own, intending to kill Bub. Logan stands between them, protecting Bub.
Bub is later seen with Logan playing with a set of headphones he has on his head. When Logan tries to adjust the headphones for him, Bub instinctively grabs his arm before letting him go, showing his trust in Logan. Logan adjusts his headphones, while teaching him how to play the tape recorder. The music being played was "Ode To Joy." By Beethoven, music Bub seemed to enjoy. When Logan shut it off, Bub was at first saddened, but per Logan's teachings, learned how to play the tape himself so he can listen to it whenever he wanted. After Logan makes his note, he turns off the recorder to tell him, that it's time for his reward. Unbeknownst to both of them, this particular demonstration is observed by Sarah and William "Bill" McDermott, who came to the lab to get morphine for the bit Private Miguel Salazar.
They discover much to their horror, that Bub's reward for being docile is being fed human flesh as positive reinforcement. Matters get worse when Rhodes walks in an discovers the travesty. They discover the source of the flesh is the remains of soldiers that have been killed, prompting Rhodes to shoot Logan killing him. Bub is later seen locked up with another Ghoul and he figures out how to get the chain off his leash, freeing him. While that is going on Miguel in a frenzy has lead a horde of the dead into the facility prompting everyone to scatter. When Bub goes to show what he learned, he discovers Logan's corpse in the freezer. When he realizes Logan is dead, he becomes grieving and enraged.
He discovers Sarah and Ted's discarded guns and picks one up. When Steel tries to flee for his life, he runs into Bub. Bub who recognizes Steel tries to shoot him. He misses and Steel flees into one of the rooms, trying to get the drop on Bub. Before he can, the horde surrounds him and he shoots himself before they could devour him. When Rhodes heads for the Armory to get an M16, Bub ambushes him. He tries to load his gun in a panic, only to drop his clip when Bub shoots at him. Rhodes attempts to flee, but gets shot in the left shoulder crippling him. When Rhodes tries to further flee, Bub shoots him in the leg, prompting him to crawl his way to the nearest exit. When Rhodes manages to get to his feet and at an unlocked door, he is greeted by more of the dead. He tries to turn back only for Bub to shoot him in the stomach. The horde devours Rhodes before Bub mockingly salutes him. Bub leaves, never to be seen again.
- Captain Henry Rhodes: Multiple gunshot wounds and left to be devoured by the horde of the dead.
Initially, Bub had the typical mentality of any other rabid zombie; however thanks to Logan's training and reeducation, Bub has regained some human intelligence. Logan concluded that Bub was able to unlock his memories from before his death and transformation into a zombie, as seen when Bub recalled how to use a razor to shave his face despite Logan never showing razors to Bub before. His intelligence continued to develop; Bub was able to speak a mumbled sentence, and his intellect even allowed him to operate and use a pistol. Later he would escape his chains by loosening an exposed screw, and accurately concluded that Rhodes was responsible for Logan's murder.
Bub's relationship with Logan improved to the point where he identified him as a friend instead as food; he made no attempt to attack Logan and trusted him entirely. Bub was still hostile to other humans however, and attempted to shoot Rhodes with an empty pistol. After discovering that Rhodes murdered Logan; Bub was distraught, crying, and sought revenge against Rhodes. Finally, as Bub watched other zombies devour Rhodes, he taunted the captain with a military salute instead of joining the other zombies in their feast.
- Bub is the third zombie in the series seen carrying a gun; The first was the zombie who took Roger DeMarco's assault rifle, and the second was the undead Stephen Andrews.
- Bub is also the first zombie in the series seen aiming and firing a gun.
- Much like Big Daddy, Bub is never seen attacking a living human for food, and thus only kills the main human antagonist as an act of revenge. Bub did, however, consume the butcher flesh and organs of the recently deceased Pvt. Johnson and Pvt. Miller given to him by Dr. Logan, implying he has not entirely lost his taste for human flesh.
- Dr. Logan stated that he named Bub after the former's father.
- At the beginning of "Land of the Dead" when Cholo is taking the box of champagne from the fridge, a zombie that strongly resembles Bub lunges at him. You can see a collar still intact from the original DOTD.