A TMZ report revealed Monday that when officers from the L.A. County Sheriff's Office visited Bieber's mansion last Tuesday, they discovered a "trove" of drugs.
"Back in my generation, we wrote the book on abusing drugs and alcohol, and many of the friends and colleagues are now dead and gone because of the way we lived," wrote Angelo in an open letter to Bieber. "I never thought for a minute my friends Jimi Hendrix or Janis Joplin would die in 1970s from drug overdoses.
"Did I learn from their mistakes? No! Did I think anything bad would happen to me? No! However, everything came to an abrupt end for me 10 years later when the cops handcuffed me to a chair in the backyard of my house in Miami. My party was officially over."
Angelo, who went on to write a book about his wild life and eventual fall, titled Once Life Matters: A New Beginning, warned Bieber that he needs to pause and take heed of some good advice, explaining he was sending him a copy of his book.
"I am sending it to you today, hoping that after you read it, you will discover some valuable insights on what may happen to you in the future if you continue to abuse drugs," Angelo wrote.
"You are a very young man, Justin, who still has a lot to learn," he continued. "When I look back to when I was your age I can remember never wanting to listen to anyone who was trying to tell me what I was doing was wrong.
"Right now, I am 67 years old. When I was 35, while riding high in the entertainment business, I suffered a major consequence for my out-of-control lifestyle. In 1980, I was arrested and pled guilty to two counts of possession of cocaine and was sent to prison for six years.
"Abusing drugs will bring you one of three definite consequences: prison, serious hospitalization or death. Please learn from those of us who have been down this road before it is too late."
Read Angelo's entire open letter to Justin Bieber here.
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