Detective O'Brien

Detective O'Brien is the quaternary protagonist of the 2015 film Terminator: Genisys.

Terminator Genisys
O'Brien is a LAPD officer who in 1984 first encountered Kyle Reese fleeing from the T-1000. His partner was killed by a T-1000 before Sarah crashed into the store and took off with Kyle. So traumatized by this event, O'Brien wanted to make sure that he understood the entire incident.

Later on in 2017, due to his age he no longer works as a street officer but as a detective he meets Kyle and Sarah again and the police are aiming to arrest them just like O'Brien originally aimed to arrest Kyle. O'Brien then started begging the authorities that he works with to release Kyle and Sarah, knowing that the two are aware of a serious danger (Skynet a.k.a. Genisys) and are working to stop it from killing off people. Once the T-3000 started becoming the real problem for authorities, he went to go release Kyle and Sarah and had them escape with the Guardian T-800 on a helicopter.