Federal charges have been filed in a pair of back-to-back armed robberies of Twin Cities letter carriers late last year, twin harrowing encounters that were the focus of a weekend rally in downtown Minneapolis.

Prosecutors last week charged Rubin David Adams, 26, of St. Paul, with robbing two mail carriers in November less than 24 hours apart in Edina and Brooklyn Center. He is also awaiting trial in Georgia on identity theft and fraud charges.

The two armed robberies received heightened attention at a Sunday rally outside the Minneapolis U.S. Postal Service building in which letter carriers shined a light on worker safety amid a spate of more than 2,000 violent attacks nationally since 2020.

The new federal charges filed in Minnesota against Adams, spelled out in a 25-page criminal complaint, outline an exhaustive investigation that yielded insight into the motivations behind the rash of postal robberies.

In a statement Monday, U.S. Attorney Andrew Luger called the case "part of an alarming trend" around the country and Twin Cities: "We take this issue very seriously and will continue to ensure postal employees are safe and free from violence as they serve their communities."

According to an affidavit last week by an inspector with the U.S. Postal Inspection Service's Twin Cities field office, investigators used location data from an ankle monitor worn by Adams as part of his Georgia release conditions to place him at the scene of the November robberies and frequent follow-up stops at mail collection boxes in Brooklyn Center.

According to the inspector, criminals seek out "arrow keys" carried by some mail carriers because they can be used to steal mail, cash or checks from mailboxes. Those checks are then often counterfeited or circulated online, and the stolen arrow keys can also be put up for sale.

Adams is being blamed for a pair of robberies that started on Nov. 18 in Edina, where a letter carrier said a man approached him in his postal service vehicle and demanded the "mailbox keys" at gunpoint. The victim told police that he did not have such keys but handed over two sets of USPS vehicle keys.

The next morning, in Brooklyn Center, police responded to an armed robbery of another letter carrier who said he was robbed at gunpoint while completing his route. The victim said his assailant left with two arrow keys.

Officers matched license plate recognition data for a Gray Chrysler 300 captured about a mile from the crime scene shortly before the robbery. Minneapolis police and Hennepin County Sheriff's Office officials later tried to stop the vehicle, but it fled the scene before crashing. Multiple suspects fled but investigators searched the abandoned vehicle, locating a set of USPS vehicle keys taken during the Edina robbery and a latch belonging to a Glock pistol case.

They also found a birth certificate in the name of Roc Adams, and a printed photograph of a counterfeit Minnesota driver's license with Adams' picture.

Investigators identified Rubin Adams as the older brother of Roc Adams, and found social media posts allegedly advertising fake driver's licenses. In videos shared late last year, Adams allegedly held stacks of cash or solicited people interested in stolen checks. Location data showed Adams' phone had been at or near the two letter carrier robberies.

According to the complaint, Adams is on probation out of Fulton County, Georgia, on state convictions for receiving stolen property, possessing a firearm during a felony, possessing a firearm as a convicted felon, and six misdemeanor offenses. He was sentenced to probation in August 2022 and jailed on a probation violation between Oct. 10 and Nov. 9.

He's also on pretrial release out of Fayette County, Georgia, on pending fraud and identity theft charges. He must wear a monitoring device as part of his release conditions, according to court documents, and investigators used location data from the device to track him within feet of the two November robberies in the Twin Cities.

Adams — whose Minnesota criminal history includes felony convictions for reckless discharge of a firearm, theft, and first degree aggravated robbery — made his first appearance on the armed robbery charges in court on Friday. There, he was ordered temporarily detained pending a full detention hearing and preliminary examination scheduled for Tuesday in Minneapolis. Messages were left seeking comment from two attorneys listed for Adams in the new federal case.

Inspector in Charge Bryan Musgrove of the U.S. Postal Inspection Service said Monday that the case was a "tremendous example of how local, state, and federal partners can join together to quickly and safely resolve situations like this."

"Mr. Adams's alleged crimes showed blatant disregard for human decency and overall greed," Musgrove added in a statement.

Charges in such cases are rare. Patrick Johnson, regional national business agent for the National Association of Letter Carriers, said at Sunday's rally that there were more than 30 assaults on letter carriers in 2022 and 2023 in Region 7, which comprises Minnesota, Wisconsin and the Dakotas. Among them was the shooting death of Milwaukee letter carrier Aundre Cross in December 2022.

But, Johnson said, only 14% of assaults on letter carriers nationwide have resulted in prosecution.

Star Tribune staff writer Greta Kaul contributed to this report.