Normally, the performer of the action (= the doer) comes first and is the SUBJECT of the verb. We then use the active form of the verb. The other person or thing is made the object of the verb.
Example: An LAPD police officer arrested Amanda Bynes last night.
But, if you want to focus on the person or thing affected by the action, you make the person or thing the subject of the sentence and use the passive form.
Example: Amanda Bynes was arrested by an LAPD police officer last night.