Charles Washington, 43, was arrested in June, and indicted Wednesday, on charges he and associates set up a sophisticated system to steal money from the bank and home-equity accounts of 16 high-income residents at several Boston area banks.

The US Attorney's office in Boston charges Washington gained access to the account numbers, other personal information and sample signatures from these account holders, then found "runners" who looked like the individuals and practiced forging their signatures before going to their banks to make a number of withdrawals over several days.

At least two Massachusetts customers of Santander Bank had more than $200,000 illegally withdrawn from their accounts, according to an affidavit by an FBI agent who participated in a lengthy investigation that started not long after those withdrawals in 2013.

Neither the US Attorney's office nor the affidavit explained how Washington gained access to the information and signatures. However, his case is being prosecuted by an assistant US Attorney who specializes in cybercrime. The affidavit leaves open the possibility of additional arrests through repeated references to the "runners" who worked for Washington.

Officials say that in addition to impersonating bank customers, Washington's minions would set up bank accounts, sometimes in their own names and sometimes in the names of bogus companies, which they would then use to arrange electronic transfers from their victims' accounts.

On April 28 of this year, investigators armed with a search warrant entered a Greenbrier Street apartment rented by Washington's girlfriend, where, they say, he spent considerable time - and where they found evidence against him, including handwritten notes with the names, Social-Security numbers, addresses, and birth dates of possible victims and notes with account numbers at Bank of America, Webster Bank, Citizens Bank, Santander Bank and TD Bank.

Also seized: Account opening kits, starter checkbooks and debit cards in the names of people who were neither Washington nor his girlfriend, two bundles of $2,000 in cash wrapped in Bank of America bands and several cell phones.

According to the affidavit, "The seized cell phones contained, among other evidence, records of calls to various bank customer service numbers and text messages that:

"a. Sent and received names, addresses, dates of birth, and Social Security Numbers;

"b. Sent and received accountholder names and bank account numbers, including business account names such as "[Name] Property Management" or '[Name] Bath and Kitchen Consultant', and '[Name] Title Company.' "

Any action in Washington's case could be delayed because last Friday, his lawyer asked to withdraw from the case because, the lawyer wrote, Washington fired him.