Bill Williamson was born in 1866. At some point, Bill joined the military before becoming a member of the Van der Linde gang. During his time in the gang, Williamson, along with Dutch and Javier, seemed to have had a casual sexual relationship with Abigail Marston. In 1906, a botched bank robbery leaves Marston wounded and disillusioned. Some time afterward Dutch goes into semi-retirement and Williamson, insane and disillusioned from Dutch's insanity, established his own gang whom resided in Fort Mercer.
Red Dead Redemption II
An ex‐soldier discharged from the army, possibly dishonorably. Hot-headed, he tends to act first and think later but is tough, dedicated and always ready to fight.
—Description by Rockstar Games.
Red Dead Redemption
In 1911, Marston has been extorted into hunting down his former brothers in arms, with Bill Williamson being the first target. The hunt for Bill Williamson serves as the impetus for the game's plot and is the central motivating factor throughout the first and partially second act.
New Austin chapter
John and Bill meet once again at Fort Mercer. John has been extorted into pursuing and apprehending Williamson due to his gang's vicious crimes. Edgar Ross and the Bureau of Investigation threaten John's son and wife to force John to complete the task. Marston confronts Williamson from outside the fortified walls, appealing to him to surrender before any harm befalls him. Williamson refuses, has several men put Marston at gunpoint, and berates John for his reformation. John responds by reaching for his revolver, causing one of Williamson's men to open fire and wound him in the lower-right torso. They presume John dead and leave his body to the elements. Hours pass, until ranchers, Bonnie MacFarlane and Amos discover him wounded. Bonnie and Amos altruistically take Marston to Nathaniel Johnston, the Armadillo doctor, to treat his wounds. John then recovers quite well after the bullet is removed. In return for a $15 doctor's bill, John agrees to work at the ranch for a short time. However, Bill later discovered that John was alive and living with Bonnie. As revenge, Bill and his followers burned the Macfarlane's barn to the ground.
During that time, Marston recruited some people in New Austin with a cost of helping them. After helping Leigh Johnson, Nigel West Dickens, Seth Briars and Irish, John planned a strategy to raid Bill's hideout. The group breached the fort only to find out that Bill fled to Mexico with the help of another of John's former gangmates, Javier Escuella. The pair was put into the Protection of the local state government.
Nuevo Paraíso chapter
John eventually ventured to Mexico himself and was forced to work with Colonel Allende, the brutal dictator of a region in Mexico called Nuevo Paraiso. Even though Allende promised to deliver Escuella and Williamson to Marston, Allende betrayed Marston and attempted to kill him. Due to the betrayal, John joined with the anti-government rebels led by Abraham Reyes and attacked Allende's villa in Escalera.
Williamson is killed during the battle in the mission "An Appointed Time" while attempting to escape with Agustin Allende in an armed stagecoach. John and Reyes ambush and disable the stagecoach before they could escape. Allende betrays Bill by pulling him out of the stagecoach and pinning him to the ground. Attempting to bargain with Marston and Reyes by trading Bill's life for his own. Both Williamson and Allende are then gunned down by John Marston and Abraham Reyes. If Marston hesitates to shoot Bill, Reyes will shoot Allende first. Bill will begin to approach John claiming that he has surrendered and will "come quietly" before suddenly reaching for his pistol. To which he will be shot dead by either John or Reyes. Edgar Ross and Archer Fordham are informed about his death and require John to return to Blackwater.
That man is a stone-cold killer.” “Williamson is a proud fool.
Bill Williamson is a ruthless and ambitious man, power-hungry, self-serving and greedy by nature, as well as lacking any morals or conscience. His ruthlessness and immorality were shown through countless acts of crime and intimidation, including arson, kidnapping, murder, and likely rape.
Throughout his life as a criminal, Bill became both respected and feared by the people and criminals of New Austin, with Bonnie even calling him "the worst bandit in the county". Many criminals and bandits such as Norman Deek chose to follow Williamson, making him one of the most dangerous and powerful criminals in the area.
Originally a friend and brother-in-arms of John, Bill's friendship with him soon turned into rivalry over Dutch's attention. By 1906 their rivalry evolved into hatred, and Bill, along with the other fellow criminals, left John to die in a miserably failed robbery.
Despite his cruelty and inhuman acts throughout his career, Bill is - truly - a coward in heart, without any sense of loyalty for his comrades or associates. During each of his encounters with John throughout the events of Red Dead Redemption, Bill never fights directly against his former friend, preferring to send his men after him instead. Bill is also quick to run away upon understanding the threat upon his life and will do anything to escape death.
Bill appears to have been less educated than John and Dutch, taking offense at John's larger vocabulary in their first encounter at Fort Mercer. Namely, the word "implore."
Bill is partly bald, revealed during his final appearance, when Allende shoves him out of the wagon, his hat falls off, revealing his baldness. It can also be seen by shooting off his hat, or by playing Poker or Liar's Dice with him in Multiplayer.
Most, if not all, of Bill's multiplayer quotes, seem to be directed at John.
The pin which holds the side of Bill's hat up bears the symbol of the Freemasons (The Square and Compasses).
The name William Williamson suggests that he has a Welsh heritage since giving one's children the same first and surname was a tradition in Wales in the 17th-20th centuries.
In Undead Nightmare among the writings on the walls of buildings in Blackwater one writing reads "Things are different now." These are some of the words that Williamson said to John before wounding him at Fort Mercer.
His name could be a reference to famed Italian Western film director, Sergio Leone, who for his early films, went by the screen name of Bob Robertson, which is similar to Bill's name in that the last name is the same as his full first name with 'son' added on the end (e.g. Robert Robertson-William Williamson).
In an interview with Retroplayer, Steve J. Palmer the voice actor of Bill Williamson; compared the relationship between John Marston and Bill Williamson to that of siblings. With Dutch being more of a "parental figure." While stating that Bill was envious of John's relationship with Abigail and bitter that she chose Marston over him. Steve went on to say that John was once a positive moral influence on Bill and that once John left the gang, Bill began to "tailspin out of control." without John's moral support.