Most Helpful Guy
Highly likely it's about the drugs. Drugs changes you. You lose your moral views and things you thought you would never do suddenly doesn't seem bad. You become insensitive to everything and everyone and all you care about is the drugs.
That's what I think since you said he began using. Otherwise he maybe just can't handle you because he struggles with other things. Or he is mad/upset that you left him and he does this stupid thing in return to show it.
Most Helpful Girl
Maybe you can lodge a report against him. That will teach him how to be an adult