Continuity mistake: When escaping out of the parking lot, John drives past the same blue pick-up truck twice.
Continuity mistake: During the truck scene, when the truck has just come off the bridge, notice the sign on the right hand side says "24 hours." Seconds later the sign seems to have mysteriously disappeared.
Continuity mistake: During the pool fight scene, you can see there's an orange ball next to the upper left pocket. In following shots it's no longer next to it and it has a dark ball in front.
Continuity mistake: John Connor comes out of the parking lot and appears right in the middle of the truck's lane, making the driver swerve to his left. From a close-up, the driver turns the wheel and straightens the truck and keeps on driving, but the following wide angle shows the truck swerved and the driver straightening it again.
Answer: He didn't steal his clothes, but copied them. He can only copy things that he physically touches. He had to touch the cop to take on his look. Also since the cop was a witness to this ruthless killing machine, it needed to kill him to protect itself from being discovered too soon. The Terminator is an infiltration unit on an assassination mission to kill John Connor. As advanced as it is, it needs as little attention drawn to it as possible. Having the entire police force chasing him down would not be ideal for his goal to get Connor and would inevitably slow him down and risk allowing Connor a better chance of escape. The T 1000 also is an emotionless machine programmed by other machines that are intent on killing off all humans in the future. It doesn't value human life, and if anything has been programmed to regard them as a pest to be dealt with. The cop was a means to an ends and an obstacle to take out. As well, the cop did also posses a weapon, and was the T-1000's quickest way to get his hands on a gun.
Quantom X ★