As reported last Thursday by TMZ, the actor, who played Fezco on the beloved HBO hit, "died from a lethal combination of fentanyl, cocaine, methamphetamine and more in what's being ruled an accidental overdose."
A source close to the family told the outlet that Angus had been struggling with suicidal ideation since burying his father the week prior.
"My son and his twin sisters were deeply grieving about their dad," Lisa shared. "They were all devastated."
In regards to his overdose, Lisa told People that "it was predominantly central nervous system depressants" found in his system. "It started to slow his heart and slow his breathing. He got tired from lack of oxygen."
"Everything just slowed down, and eventually his heart stopped and he went to sleep," she explained before making it clear that her son did not take his own life. "But he didn't kill himself."
While it's been difficult, Lisa said that the overwhelming support from Angus' fans have helped her and her family cope with his sudden passing.
"He went out at his total power, his total beauty, his total influence, and the reaction that everyone has had is very moving to me," she said. "You know, he's not just an actor who overdosed. He was a beautiful soul, and that's why people miss him so much."
Reflecting on the mark he left behind, Lisa said her son will "always shine bright."
"I always knew he was special and I'm so glad the world also found out he was special," she shared. "My son will always shine bright."
If you or someone you know is struggling with substance abuse, get help. The Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline (1-800-662-4357) provides 24/7, free, confidential support for people in distress.
If you or someone you know is struggling with depression or has had thoughts of harming themselves or taking their own life, get help. The National Suicide Prevention Lifeline (1-800-273-8255) provides 24/7, free, confidential support for people in distress.