How to take legal action against my ex for harassing and blackmailing.

I doubt that my ex bf has not deleted my pics yet and he could misuse them. when i logged into his account and i saw that he has not deleted my pics so i deleted his account .then he started calling my friends and on my parents number. he was accusing me that i did cyber crime by deleting his account and he was harassing me and blackmailing me. he even started sending spam messages on my phone number then to retaliate i did the same. i tried to contact his parents but he changed their phone numbers. i fear that his friends also might have pictures of me so i asked him to ask them to delete. he said that he is not accountable for them. his friends are like him. they sexually abuses girls and one of his friends tried to sexually abuse me and my ex did not do anything about it and that time i was minor and there was 1 other boy and 2 girls also and even they did not do anything about it. they were minor too. Guide me what should i do? now im an adult and i don't want to involve my parents. but i want to sure that he and his friends do not have any pictures of me.