Almost one year ago, in broad daylight, North Miami postal carrier Bruce Parton was killed for his key — a master key, authorities say, that unlocked personal financial information to residents of a North Miami-Dade condo building.

The two men charged with the 60-year-old’s murder used his so-called Arrow Key to steal the information from dozens of residents’ mailboxes. Like magic, the pair converted the identities of others into an electronic stream of cash, by filing fabricated income tax returns in the victims’ names over the Internet, according to court documents.Their unwitting accomplice turned out to be the Internal Revenue Service. The IRS, without verifying their false income claims, loaded the refunds onto debit cards the men allegedly used in others’ names at Winn-Dixie supermarkets, 7-Eleven convenience stores and Chase Bank, records show.

Pikerson J. Mentor, 30, the alleged triggerman who had just been released from prison before Parton’s death, and Saubnet Dwayne Politasse, 23, the accused getaway driver, have joined a disturbing trend of street criminals who have entered the growing ranks of identity-theft scammers, authorities say.

Both Miami-Dade men, who are being held in federal custody without bond, pleaded not guilty this month to new aggravated ID theft charges — along with homicide, use of a firearm, carjacking, robbery, debit-card fraud, unlawful possession of a postal key and, in Mentor’s case, possessing ammunition as a felon.

The U.S. Attorney’s Office and federal agencies won’t comment about the Dec. 6 murder of Parton. The Justice Department is considering whether to seek the death penalty.

But authorities say the case is a dramatic example of identity-theft crimes that have soared in the electronic age. Crooks have graduated from everyday credit-card fraud to stealing people’s identities such as Social Security numbers in order to rob refunds from taxpayers before they file their returns with the IRS.U.S. Attorney Wifredo Ferrer said he expanded a federal task force from Miami-Dade to Broward early this year to fight identity-theft crimes in the region, where prosecutions of defendants have quadrupled to nearly 90 since 2007, court records show.

“We are seeing defendants once involved in other types of crimes [such as drug trafficking] getting involved in identity-theft schemes, because it’s easy to do, lucrative and less violent,” Ferrer told The Miami Herald.

Ferrer said the tax-return rackets are particularly pernicious because they harm two victims: legitimate taxpayers whose identities and refunds are stolen — plus the federal government.

“I’m seeing this as a real threat because we’re dealing with a massive program,” he said.

Indeed, the epidemic of identity-theft and tax-return fraud has spread not only in South Florida but nationwide.

In September, for example, federal agents arrested 49 people — several with criminal records — in the Tampa area on charges of stealing identities and using them to obtain fraudulent tax returns. Investigators in Operation Rainmaker, as the year-long probe was dubbed, intercepted $100 million and recovered $5 million in fraudulent refunds, cash, jewelry, cars and entertainment systems.

Here’s how the scheme worked: After making sure a person’s stolen Social Security number was not used on a tax return, a suspect filed for a refund through online companies such as Turbo Tax. A tax refund was then issued with a prepaid debit card, check or direct deposit.