Adult temper tantrums? Rage? Anger? Who can help someone with them and not inform authorities?

Seek Tx. Usually information you provide during treatment stays confidential. However, there are some limits to confidentiality with being in danger to yourself or others are some of them. If you feel you cannot control your sx anymore, either dial 911 or go to the nearest emergency room. Otherwise, you might want to consider making an appointment with psychiatrist and psychologist to start your treatment.
Tantrums are not. age-appropriate in adulthood. When calm, explain that you will not engage when (s)he is tantruming - no talking, glaring, yelling, no positive or negative attention of any kind. If that person refuses to seek psychiatric care & his/her behaviors pose a danger to him-/herself or others, arrange involuntary commitment to a mental health facility instead of enabling the person to hurt someone.