He said one sentence then shut his mouth and didn't speak again.
Tips
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Sharp / rude as a command — 闭嘴! is 'Shut up!', not 'be quiet.' Softer alternatives: 安静 (ānjìng, 'quiet'), 别说了 (bié shuō le, 'don't talk anymore'). 给我闭嘴 is even more aggressive (the 给我 adds bite).
mistakes
Don't use 闭嘴 to politely ask classmates or coworkers to be quiet — it lands like 'shut your mouth.' Use 安静一下 or 小声点 instead.
