Billionaire banking heir and private equity investor Matthew Mellon died Monday in a drug rehabilitation facility in Cancun, Mexico, his family said in a statement. The 54-year-old was reportedly addicted to OxyContin — a time-release version of oxycodone, which has long been the world's top-selling opioid painkiller.

“Billionaire Matthew Mellon, 54, died suddenly in Cancun, Mexico, where he was attending a drug rehabilitation facility. Mellon made his fortune in cryptocurrency, turning a $2 million investment into $1 billion. He is survived by his three children, Force, Olympia and Minty. "The family asks that their privacy be respected at this very painful time,” the family's representative said in the statement. The exact cause of death remains unknown.

According to Page Six, Mellon reportedly spent $100,000 a month on OxyContin and took about 80 pills a day. In 2016, the entertainment website reported that Matthew blamed his doctors for the addiction, saying they were "writing prescriptions like they were Smarties."

At the time, Mellon was checked into Passages Malibu, an addiction-treatment center, and said he was determined to battle his demons.

OxyContin has been blamed for launching the opiod empidemic now gripping the USA. Millions misuse the drug to get a heroin-like high by crushing the pills and snorting or injecting the  dose. Excessive use of OxyContin can lead to serious, life-threatening, or fatal respiratory depression. Those prescribed to use OxyContin are instructed to swallow tablets whole as crushing, chewing, or dissolving the tablets could cause rapid release and absorption of a potentially fatal dose of oxycodone, according to reports.

Common side effects of OxyContin include nausea, vomiting, constipation, loss of appetite, dizziness, headache and tired feeling. Other effects include shallow breathing, slow heartbeat, seizure (convulsions) and severe weakness.

Mellon, a former chair of the New York Republican Party’s finance committee, told Page Six that he was prescribed OxyContin after he suffered from a surfing injury.

Mellon, a graduate of the Wharton School of the University of Pennsylvania, married his first wife Tamara in 2000. She earlier said Mellon suffered from a cocaine addiction during their marriage. The duo has a daughter together named Araminta aka Minty.

Mellon later wed Nicole Hanley with whom he has two children —  son, Force, and daughter, Olympia. Mellon and Nicole announced their split in 2015 after an attempted reconciliation. After getting divorced, Mellon partied in a luxury Los Angeles mansion that he rented for $150,000 month.

When he began dabbling heavily in cryptocurrencies years ago, his friends and family tried to dissuade him, figuring it was another erratic obsession."Crypto is scary and dark. It's anti-America," Mellon told Forbes. "I am pro-America, pro-business and pro-bank. That's why I went with Ripple."

"It's $1 billion virtually for free. I actually have earned it because I was the only person who was willing to raise his hand," Mellon said at the time. "My family thought I was insane, when I knew it was a home run."