A Minneapolis man admits going on an armed robbery spree with others, hitting four Twin Cities pharmacies in a matter of weeks and making off with hundreds of doses of oxycodone and other powerful painkillers.

Michael B. Bynum, 31, pleaded guilty Monday in federal court in St. Paul to holding up the West 7th Pharmacy in St. Paul in April 2012 and stealing more than a pound of oxycodone, plus other drugs.

It was Bynum’s fourth pharmacy robbery in about six weeks, with the string being snapped once police arrested him and two cohorts after a brief pursuit.

Bynum also admitted holding up Lloyd’s Pharmacy in St. Paul on Feb. 18, 2012, the Best Aid Pharmacy in St. Louis Park on March 15, 2012, and the Pro Pharmacy in St. Paul on March 27, 2012.

Authorities say smaller pharmacies are favored targets for robbery because they have less security, fewer customers and are easier to case.

In September, Ray J. Brown, 24, of Minneapolis, admitted to his role in the four robberies. His brother, Rayshawn E.J. Brown, 21, also of Minneapolis, admitted to the West 7th and Pro Pharmacy holdups.

According to court documents:

The Browns donned gloves and masks, then entered the West 7th Pharmacy. Ray Brown pointed a .40-caliber semi-automatic pistol at employees and ordered them to drop to the floor.

He directed the pharmacist to put Percocet, Vicodin and oxycodone into a bag and hand over the drugs. The Browns fled into a waiting car. Bynum, who is paralyzed, was behind the wheel.

Police stopped the car, and the Browns fled on foot. Ray Brown was quickly caught. Rayshawn Brown was arrested about an hour later, emerging from a house and claiming to be homeless and living under the porch.

According to statements made to police by both brothers, Rayshawn Brown had seen his brother with money “and asked how he could get some.”

In the Pro Pharmacy robbery, the Browns fled with more than 300 oxycodone pills. The drugs were sold later for about $1,100, Ray Brown told police.