Here, the subject of the sentence is the police, and the object of the verb is the criminal. In a sentence with passive voice, you need to have the object of the verb in the front of the sentence. The subject is optional. You can rearrange the sentence like this if you would like:
- The criminal was ordered to be shot (by the police).
Whether or not you add the last part (by the police) is up to you! However, the sentence works well either way.
