Place it just after the scare in an edit, following Sudden Suspense for the build-up and letting Oh My God Wow carry the bigger reaction that comes next, so the edit moves from tension to this reaction to a louder response.
Über diesen Sound
This is a short spoken reaction, lasting about two and a half seconds, in which a voice admits to being scared in the moment. The delivery is startled and sheepish rather than dramatic, which makes it feel honest and relatable.