Translation of "Dumbfounded" in Japanese

Tom is dumbfounded.

トムは唖然としている。

When I heard it, I was dumbfounded.

私は呆気にとられた。

- The news paralyzed him.
- When he heard the news, he was dumbfounded.

そのニュースを聞いて彼はぼうぜんとした。

- They were stunned after finding out about his resignation.
- They were dumbfounded by the news of his resignation.

彼の辞任を知って、彼らは呆然とした。