Tā sǒngjiān biǎoshì zìjǐ bù zhīdào fāshēng le shénme.
She shrugged to indicate she didn't know what had happened.
Tips
usage
耸肩 is often reduplicated as 耸了耸肩 to describe a single, brief shrug gesture. It conveys indifference, helplessness, or 'I don't know' — the same as its English equivalent. The verb 耸 (sǒng) means to raise or hunch up.