The "Euphoria" actor's mother, Lisa Cloud, took to Facebook to pen an emotional message, writing ... "Friends, I want you all to know I appreciate your love for my family at this shattered time. I also want you to know that although my son was in deep grief about his father's untimely death from mesothelioma, his last day was a joyful one."

She goes on to describe was Angus was doing that day, saying he was reorganizing his room and placing items around the house ... which she believes meant he had an intention to be around for a while. Lisa also says he'd been talking about wanting to help family members with college, among other signs that -- in her eyes -- point to him not being suicidal.

Then, Lisa says this point blank ... "I don't know if or what he may have put in his body after that. I only know that he put his head on the desk where he was working on art project's, fell asleep and didn't wake up. We may find out that he overdosed accidentally and tragically, but it's abundantly clear that he did not intend to check out of this world."

She adds, "Social media posts have suggested his death was intentional. I want you to know that is not the case. To honor his memory, please make random acts of kindness part of your daily life."

It's interesting that she's batting down any notion of suicide. Not only did a family statement released at the time suggest he died by suicide ... but sources familiar with the situation have further assured us that Angus was, indeed, having suicidal thoughts of late.

Unclear if there's more evidence to indicate he may have taken his life -- like a note, for example. In any case, his mother's backing that he was in high spirits -- which we've seen ourselves -- in his final days ... despite having a hard time dealing with his father's death.

BTW, Lisa appears to have been on the scene in Oakland when Angus was found ... first responders cited her as being the one who called 911 that fateful Monday morning.

He was 25.