Zimmerman. Returning to Sing Sing. Either because he escaped or was released.
And probably dealing with a whole fuckton of disorientation. Jackie realized too late that shining a flashlight and calling out to someone whom she wasn't fully familiar with was a bad idea. She didn't turn the light off – it was dark and the moon was only so bright – but she did aim it at the ground at her feet, effectively taking away the threat of shining a spotlight on him and allowing him a better view of her.
Her training had taught her how to keep people calm in frantic situations. This was no different from that. Until she had reason to believe otherwise, she had to assume David had escaped from his captors and, thus, the panic in his voice was justified. Her intent had to be to keep him from bolting,
Jackie didn't move from where she was standing. His reaction spurred her into shoving her own startlement aside and focusing on what was happening now. “I'm not. I'm staying right where I am. I'm not going to hurt you,” she spoke calmly, clearly. “You're safe.” As safe as he could be among zombies, anyway.
Whether he believed her, whether his mind was stable enough to understand, would be up to him. Jackie would do what she could to reassure him, but nothing compared to the trust of someone he was close to. Her thoughts immediately went to Ellie. She wasn't very close to that young woman either, but she'd known how close the couple had been.
“My name's Jackie. I live in the compound. I was heading back there when I saw you.” Again, spoken in the same level tone. “How badly are you hurt?” She didn't ask where he'd been right away. The more important question came first.