This T-1000 was sent to the year 1973 to kill Sarah Connor when she was only 9 years old. He was only able to kill her parents and his mission was compromised when a T-800 from an unknown point in time arrived and rescued the young girl. 
After the arrival of Kyle Reese in 1984, the T-1000 disguised as a police officer arrived at the place where Kyle was and chased him into a department store. Shortly after Officer O'Brien and his partner showed up, he hid inside a large mirror before attacking Kyle and the two officers until Sarah Connor came to the rescue of Kyle.
The T-1000 continued its pursuit of Kyle Reese, Sarah Connor and Pops with a piece of itself as a tracking device from the back of their ambulance. The T-1000 was lead to an abandoned warehouse where it impaled the Guardian with a spear emerged from itself and then used a drop of mimetic polyalloy to reactivate the T-800 that had recently been disabled by Sarah. Despite its efforts, Kyle Reese was able to decapitate the T-800 with a Barrett 50-cal sniper rifle.
After a brief confrontation, Sarah lead the T-1000, who impersonated Kyle, into a large room with barrels of highly corrosive acid under a grate on the ceiling. It tried to confuse Sarah with the real Kyle, but she guessed (correctly) by shooting one of the Kyles in the foot. She then shot acid containers on the ceiling, which corroded the Terminator to almost the point of immobility; this did not completely stop it, as enough polyalloy remained to still form a semi-coherent form that it used to slash at Sarah. It only got a couple of strikes in before Pops, who had since freed himself from the T-1000's spike, finished it off by holding it under the acid shower until it corroded into nothing.
Behind the Scenes
- This T-1000 only has one line of dialogue in the entire film (not counting impersonations). It tells Kyle Reese, "May 12th, 1984, the day you arrived".
- It is worth noting that, in the entire Terminator film series, this T-1000 is the only Terminator sent by Skynet that does not participate in direct physical hand to hand combat with a CSM-101 portrayed by Arnold Schwarzenegger on screen. It is likely to have fought Pops off screen directly, however, this is not shown or confirmed in any way. The only times the Guardian and the T-1000 have any physical contact is when the Guardian shoots the piece of the T-1000 disguised as a lock from the door of the van; when the T-1000 pins the Guardian to a wall with a spear made from its own arm; and when the Guardian holds the T-1000 under the shower of acid until it is destroyed (although Lee Byung-hun was wearing a motion capture suit at the time and was not seen onscreen).