Aaron Carter missed rehab therapy sessions the day before he was found dead

Melanie Martin was doing her best to help him through their separate relationship

Although he kept Melanie Martin in the dark about any recent addiction struggles.

Melanie signed up him for outpatient rehab after confronted Aaron back in September

Aaron received a welfare check around that time fans worried he was huffing compressed air off-camera.

We're told that Aaron agreed to go through with the program, with the idea that it would go a long way in helping him regain some custody of his son, Prince.

Sources say he put the schedule on hold but was reinstated last week - he was supposed to have an online session on Friday evening, but that was not a show.

When the facility arrived to tell Melanie, she gave them the sad news.

Keep in mind, it's possible - if not possible - he missed that appointment because aaron was already dead.