Place it as the immediate reaction beat after the reveal in your edit, and build toward it with the sudden suspense sound button for tension first. Follow it with the oh my god wow sound button only for a second, bigger reaction from another person on screen.
Über diesen Sound
A four-second voice clip of a person exclaiming 'Mas que porra foi essa!?' in Brazilian Portuguese, roughly 'what the hell was that!?' in English. It lands as pure disbelief, the kind of stunned, half-laughing shock you feel when something makes no sense at all and you need a second to process it.