- "Me Ma used to hit harder than that!"
- — Brian O'Neill
Brian is the grandson of Jimmy O'Neill, who at one time ran the biggest Irish gang in the city. After his grandfather's death, Brian succeeded the position of Boss in the Irish gang.
He is first seen in Murphy's Law, when he and his crew crash through the jewelery store while Vito Scaletta and Joe Barbaro were robbing it. He was surprised to see Joe and ordered his men to kill Vito and Joe. However, several police officers arrived and had him and several of his men arrested, while Vito and Joe escaped with the jewels.
Imprisonment & Death
He is seen again in Hartmann Federal Penitentiary serving his time, where upon Vito's arrival he starts a fight with him, in which he beats Vito. During the fight, they attract the attention of the guards and both men were thrown into solitary confinement.
After a time however, Vito fell into favor with Leo Galante, the Consigliere to Frank Vinci. Vito was taught how to box and trained extensively with Leo's number one fighter Pepé Costa, who is himself scheduled to fight Brian. However, Brian had his goons jump Pepe, rendering him unable to fight. As revenge for this, Leo had Vito go to the prison gym, where Brian was working out by himself, to just break some of his bones to teach him a lesson.
Vito then began to beat Brian badly, thanks to the training he got from Leo and his men. However, midway through the fight, angered that he is losing to Vito, Brian pulled a shank and attempted to stab Vito. Vito was able to defend himself well, and turned the knife back on Brian, cutting his throat. When Brian began choking, Vito said: "Shut the fuck up!" Vito took the knife and stabbed Brian once more in the neck, killing him.
- Brian's prison number is 19475.
- Vito stated that no one ever found out who actually killed O'Neill. However, six years later, O'Neill's cousin Mickey Desmond torched Vito's home as revenge for killing O'Neill. It could have been referring to the police or the prison guards as not knowing who killed Brian. Unofficially, it could be well known throughout the criminal underworld who killed O'Neill.
- Brian seems to have some sort of antagonistic relation with Joe Barbaro.
- Brian briefly appeared in the Christmas Confession trailer, when Vito hit him in the face. However this scene takes place in some sort of warehouse, while this scene took place in prison during the actual gameplay.
- During the mall heist in the mission Murphy's Law, you can fight the mall security and Brian's crew, but Brian is invincible and cannot be killed with any kind of weapon.
- It is stated by Joe Barbaro that Brian usually works as hired muscle.