He's bracing himself for another attack, but one doesn't come. Instead she runs, and Derek would have called that good enough, except for the direction she's running in. He honestly can't be sure if she's going for her weapon or if she's heading back to the bomb again, but it doesn't really matter. He can't let her reach either one.

There's no time for him to lunge at her again, though, and he's already wasted too much of it. There's gotta be more rebels looking for her.

So he doesn't hesitate - as soon as she starts running, he pulls his gun from his hip and shoots her.