Gabriel was just looking towards Car for a moment and he questioned, "You know something?" However his attention was going towards his sister when she was tugging at the rope for a moment, and he saw that she was unlatching herself from the harness. "What the hell are you doing?" he was calling down. This had her looking up and she was commenting that she had found somebody else, although they were on the ledge a few feet below her. The rope didn't go down any lower, so the only way to get to him was to drop the last few feet.
(Think Cadet Kelly when Kelly is rappling down to get to her father, if you 've ever seen the movie)