all at once

I was reading when all at once, the lights went out.

我正在讀書，突然間燈就熄滅了。

It was raining continuously, and then all at once, it stopped.

雨一直下著，然後突然間就停了。

He was talking, and then all at once, he started coughing.

他正在說話，然後突然間開始咳嗽。