Detective O' Brien is originally a beat cop in the Los Angeles Police Department and now a detective in the San Francisco Police Department.
Officer O'Brien was presumably one of the police officers who chased Kyle Reese in the department store shortly after he arrived. He and the other officers were unsuccessful in arresting him.
Terminator Genisys timeline
Officer O'Brien was one of the two police officers to respond to Kyle Reese breaking and entering at the clothing shop. He and his partner were able to cuff Kyle after he ran into them. Shortly after, all three were attacked by the T-1000. His partner was killed while Kyle and him took cover. In order to stop the T-1000, O'Brien shot it multiple times with no effect. He was shocked and had no explanation for what he had just saw until Kyle told him it was a robot from the future. He reluctantly un-cuffed Kyle after he demanded for it several times. As moments later, Kyle escaped with Sarah Connor, who drove an ambulance into the department store to save him. O'Brien was spared as the T-1000 went after Sarah and Kyle as they were the primary targets.
33 years later after Kyle and Sarah arrived in 2017, O'Brien has now become an older police detective. He was on the team questioning Sarah and Kyle, but was convinced they were time travelers and not terrorists like his partners suspected. His partners passed this off as crazy talk, as he is a known drunk. When he saw Kyle and Sarah, he claimed that they had not aged a day since he last saw them at the shop. He gained more information about them after Kyle told him what year he was from and what situation they were in before being taken out of the room by his superior.
Later after Sarah, Kyle, and Pops were arrested due to the incident on the Golden Gate Bridge, Detective O'Brien brought the Reese family to get a positive idea for the adult Kyle Reese. He then left to witness the interrogation of Pops where he states that he had been working the entire case for 33 years. While talking with his partners, they were attacked by a disguised T-3000, who killed everyone in the room, but as he turns to shoot O'Brien, Pops grabbed T-3000, resulting in him only being wounded in the arm. As he narrowly escaped the battle, he rescued Sarah and Kyle. O'Brien wanted to help as he now knew they were trying to stop the end of the world. He supplies them with guns and ammo as Pops joined up with them. He was able to safely lead them all to a helicopter where he was thanked by Sarah. Seconds later, they were attacked by the T-3000. O'Brien was shot at, causing him to fall to the ground, but he was able to pull himself up and presumably ran to safety.
Behind the Scenes
- His name was not mentioned in The Terminator, but he was one of the cops in the department store. There were many actors to play the police officers, it is difficult to identify which actor portrayed the character.
- O'Brien's role in Genisys is similar to that of James Ellison, an FBI Agent who sees evidence about Terminators and realizes Sarah is not insane in Terminator: The Sarah Connor Chronicles.