Answer and Explanation:
If you see a crime being committed, the first action you must do is take safety, if you are in a situation that is dangerous. Once your position is safe, call 911, which will bring you to an operator to then get the police to the situation. You must be specific in details when describing the crime taken place, such as what the person/group are doing, wearing, and where they were last seen.
If the crime was done and in the past, then you can still call 911 and tell them details of the incident, in which they will build a case and find evidence as necessary.
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