The 19-year-old died from a suspected overdose after he was allegedly sold fentanyl-laced pills, according to his mother Drena De Niro, who is the daughter of Robert and his ex Diahnne Abbott.
"Someone sold him fentanyl laced pills that they knew were laced yet still sold them to him," she wrote in the comments section of a July 3 Instagram post. "So for all these people still f--king around selling and buying this s--t , my son is gone forever."
Leandro was found unconscious and unresponsive inside a New York City residence around 2:20 p.m. local time July 2, a spokesperson for the NYPD told E! News. He was pronounced dead at the scene.
Later that evening, Drena confirmed the death her "beautiful sweet angel," writing in a tribute to Leandro on Instagram.
"You have been my joy my heart and all that was ever pure and real in my life," the 51-year-old, who shared Leandro with artist Carlos Mare, wrote. "I wish I was with you right now. I wish I was with you. I don't know how to live without you but I'll try to go on and spread the love and light that you so made me feel in getting to be your mama."
"You were so deeply loved and appreciated and I wish that love alone could have saved you," she continued. "I'm so sorry my baby."
Leandro's grandfather Robert has been "deeply distressed" by the death. "We're greatly appreciative of the condolences from everyone," the legendary actor said in a statement to NBC News. "We ask that we please be given privacy to grieve our loss of Leo."
Prior to his passing, Leandro was a budding actor with credits in 2018's A Star Is Born and Cabaret Maxime—both of which he appeared alongside his mom.
"None of this is right or fair and my heart hurts in a way I never knew possible while still breathing and barely functioning," Drena shared in a July 4 post dedicated to her son. "You didn't deserve to die like this but I can only believe that God needed a strong powerful angel in their army."
She added, "I'm holding you every second of every moment I'm my heart and memories until I'm with you again. My heart is broken forever. Me daddy and your family love you, I love I love you with every beat of my crying heart."