Option 1: "They" refers to the second person in the car. The woman that called was a passenger. She says "pull up" to the driver. This driver is rumored to be a retired LEO. (Listen to the 911 call to gain full context.)
Option 2: There was a second call we haven't heard yet.
I think 1 is more likely. It'll come out in the court case if 2 is what actually happened.
There are several people (Nobel Wray for one) saying there were two phone calls. I think the fact that there were two people in the car from where the call came from has been caught up in a confusion of some sort.