Robert De Niro's Grandson Leandro's Cause of Death Confirmed 1 Month After His Death

Leandro De Niro-Rodriguez, 19, was found dead on July 2

Leandro De Niro-Rodriguez died of an accidental drug overdose, the New York City chief medical examiner's office confirmed to PEOPLE Tuesday.

The 19-year-old grandson of Robert De Niro was found dead on Sunday, July 2.

According to the medical examiner, his death was from the "toxic effects of fentanyl, bromazolam, alprazolam, 7-aminoclonazepam, ketamine, and cocaine." TMZ was first to report the news.

Days after Leandro's death, his mom Drena De Niro wrote on Instagram, "Someone sold him fentanyl laced pills that they knew were laced yet still sold them to him."

"So for all these people still f---ing around selling and buying this s---, my son is gone forever," she added.

Related: Drena De Niro Says Paul Reubens and Her Late Son Leandro Can 'Take Care of Each Other' in Heaven

In mid-July, 20-year-old Sofia H. Marks was arrested in connection to Leandro's death, accused of selling the drugs to him. Her trial is expected to begin later this month.

Robert, 79 — who recently welcomed his seventh baby, daughter Gia Virginia, on April 6 — said in a statement after his grandson's death, "I'm deeply distressed by the passing of my beloved grandson Leo. We're greatly appreciative of the condolences from everyone. We ask that we please be given privacy to grieve our loss of Leo."

When she announced Leandro's death in July, Drena said in an Instagram tribute, "My beautiful sweet angel. I have loved you beyond words or description from the moment I felt you in my belly."

"You have been my joy my heart and all that was ever pure and real in my life," the actress, 55, continued. "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. I’m so sorry my baby, I’m so sorry @carlosmare. Rest in Peace and Eternal Paradise my darling boy."

She marked one month since his death, writing on Instagram, "I think of you and long for you, every minute of every day. Never forget how happy you made so many people just by being here and being beautiful kindhearted you. Your legacy is Love."

If you or someone you know is struggling with substance abuse, please contact the SAMHSA helpline at 1-800-662-HELP.

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