A man with a long criminal rap sheet has admitted to participating in robbing letter carriers in Edina and Brooklyn Center of their work keys at gunpoint.

Rubin David Adams, 27, pleaded guilty Tuesday in U.S. District Court in St. Paul to two counts of armed robbery in connection with the holdups on back-to-back days in November 2023.

Federal guidelines call for Adams to receive a sentence ranging from slightly more than nine years to nearly 11½ years in prison. However, federal judges have full discretion when sentencing defendants and are not bound by the guidelines calculation. Adams remains jailed ahead of sentencing, which has yet to be scheduled.

U.S. Postal Service keys are not only valuable for stealing money, checks and financial transaction cards out of mailboxes, but they also can be sold to other people, according to federal officials.

Postal carrier robberies climbed to 643 in 2023, an increase of nearly 30%, and the number of robberies resulting in injuries doubled to 61 last year, according to the U.S. Postal Inspection Service.

All told, robberies grew sixfold over the past decade and the number of postal carriers held at gunpoint increased even more, according to an Associated Press analysis of postal statistics.

According to court documents:

Shortly before 3:30 p.m. on Nov. 18, 2023, Adams drove with a man to Edina and parked an SUV in front of a mail truck in the 5700 block of W. 66th Street. The accomplice approached the letter carrier, pointed a handgun and demanded any keys for a mailbox. Having none, the carrier gave the gunman keys for two Postal Service vehicles. Adams' accomplice got back in the SUV, and the two drove off.

Federal officials have not said whether the gunman has been arrested or charged.

About 9 a.m. the next day, Adams drove alone to the 6500 block of Riverwood Lane in Brooklyn Center and parked in front of a mail truck. He got out of the car, trained a gun at a letter carrier's head and stole two Postal Service mailbox keys.

Using a combination of residential video surveillance and automated license plate recognition data in Brooklyn Center, investigators determined what car Adams was driving. Late that afternoon, Minneapolis police and Hennepin County sheriff's deputies spotted the car and gave pursuit.

The car crashed at 36th and Knox avenues in north Minneapolis, where multiple occupants fled on foot. A law enforcement search of the car turned up one set of Postal Service vehicle keys, a pistol case, Adams' birth certificate and a Minneota driver's license with his photo but someone else's name.

Five days after the Brooklyn Center robbery, a Facebook video showed Adams displaying 15 checks of varying styles spread out on a countertop.

Subsequent postings on an Instagram account showed him flashing large amounts of cash and making a banking app deposit of more than $5,400.

The State Patrol pulled over Adams in an SUV on Nov. 29, 2023, on a warrant for his arrest in connection with an unrelated investigation. In the vehicle were three counterfeit temporary Minnesota driver's licenses with his photo and others' names.

At the time of his arrest, Adams was on pretrial release for identity theft and fraud charges in Georgia. He also was on probation out of Fulton County, Georgia, on convictions for receiving stolen property, possessing a firearm during a felony, possessing a gun as a convicted felon and six misdemeanor offenses.

His Minnesota criminal history includes convictions for reckless discharge of a gun, theft and first-degree aggravated robbery.

Soon after Adams was charged in January, U.S. Attorney Andrew Luger called the case "part of an alarming trend" around the country and the 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," Luger's statement read.

Staff writer Stephen Montemayor and the Associated Press contributed to this report.