“发现罪犯应该立即报告警察”用英语怎么说?

You should call the cops right away when you seen a crime.

其实楼上都是对的。
我给你写一个好的你看行不行：Report to the police department immediately when witnessing a crime being committed.
比较正规，也比较通顺。
（3楼那几个也都能用。）

report to police officers when you recognize the criminals.
cop is a low term. in north america some of rude people call police officers as "cops" or pigs
and if you are not tracing the criminals all the way down, you are not supposed to use "find".

You should report to the plice the moment you spot a criminal

祈使句：Call the police when witnessing crimes.【简洁】写在扫盲手册上的：Whenever you witness crime being commited,you should inform the police right away.添油加醋一点的：Whenever you witness crime be...

Once you find the criminal,you should report to the police at once.
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