The New York City Office of Chief Medical Examiner said Tuesday, August 8, that an accidental fentanyl overdose killed Robert De Niro’s 19-year-old grandson, Leandro De Niro Rodriguez.

ABC News has learned De Niro Rodriguez died July 2 of what the medical examiner described as the toxic effects of fentanyl, bromazolam, alprazolam, 7-aminoclonazepam, ketamine and cocaine.

The manner of death was ruled accidental.

The findings are incidentally what Leandro’s mother, De Niro’s eldest child, Drena, suspected in an Instagram post captured by TMZ.

Drena said the powerful synthetic drug was the cause of her only child’s death, noting on Tuesday, July 4, “Someone sold him fentanyl laced pills that they knew were laced yet still sold them to him so for all these people still f****** around selling and buying this s***, my son is gone forever.”

A suspect, Sophia Haley Marks, 20, was arrested weeks later at her home in Manhattan by the New York Police Department and Drug Enforcement Agency for allegedly supplying the drugs that killed De Niro Rodriguez, law enforcement sources told ABC News.

Marks was charged with one count of distributing and possessing with intent to distribute fentanyl and alprazolam, which carries a maximum sentence of 20 years in prison, and two counts of distributing and possessing with intent to distribute fentanyl, each of which also carry a maximum sentence of 20 years in prison.

Marks is allegedly known on the streets as the “Percocet Princess” and is believed to have sold drugs to De Niro Rodriguez, the sources said.

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