The Securities and Exchange Commission has charged a former investment advisor at J.P. Morgan Securities with stealing at least $20 million from customers to fund his own brokerage accounts in a scheme that spanned more than three years.

Michael J. Oppenheim, 48, allegedly used his position as a private client advisor to persuade at least two customers to withdraw over $12 million out of their accounts on the promise that he would use the money to purchase municipal bonds for their accounts. Instead, he bought himself cashier's checks and deposited them into his own or his wife's brokerage account, the SEC charges in a complaint filed Thursday.

"We allege that Oppenheim promised his customers that he would invest their money in safe and secure investments, but he seized the funds and aggressively played the stock market in his own accounts," Amelia A. Cottrell, associate director of the SEC's New York Regional Office, said in a statement.

According to the complaint, Oppenheim either spent or squandered the money in highly unprofitable trading of stocks and options in companies such as Tesla, Apple, Google and Netflix, and then attempted to cover his tracks by creating fake account statements or transferring money from one customer's account to another's to replenish funds he had stolen earlier, the SEC said.

Oppenheim could not be reached for comment. He did not immediately respond to an email sent to him via BrightScope Advisor Pages, an online directory for financial advisors.

Oppenheim worked for J.P. Morgan Securities in New York, N.Y., and was registered with Chase Investment Services, according to his BrokerCheck report.  On March 18, 2015, J.P. Morgan Chase terminated his employment, the SEC said.

"We are sorry and angry this happened. We always stand by our customers and will ensure no customer who had their money stolen will lose any funds related to this," said Michael Fusco, a spokesperson for Chase Wealth Management.

Fusco noted that J.P. Morgan Chase alerted authorities about Oppenheim's misconduct and continues to work with authorities on the investigation.

The SEC seeks disgorgement of ill-gotten gains plus prejudgment interest and financial penalties as well as permanent injunctions barring future violations.

The U.S. Attorney's Office for the Southern District of New York also announced criminal charges against Oppenheim.

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