Trio of robbers — one armed — enter CVS and demand money. But when off-duty federal cop walks in, their plans are soon thwarted.

A trio of males entered a Maryland CVS store earlier this month — one of them armed with a handgun — and demanded money and prescription medications, the Charles County Sheriff's Office said.

As the store staff complied with their demands, an off-duty federal police officer entered the Bryans Road store, after which an employee told him what was going down, officials said.

And the officer wasn't about to let them get away with it.

Swift action

Officials said the officer took immediate action, and that two of the suspects fled the store, after which the cop gave chase. The sheriff's office told TheBlaze Tuesday that the two suspects tried entering a car, and one managed to get into the driver's seat.

As the officer tried to make the arrest, the suspect behind the wheel reached for an object — and the off-duty officer, fearing for his life, fired his gun. No one was struck, officials said, but the suspect took off in the vehicle.

The other suspect who ran out of the store ran back in, officials said, and local law enforcement showed up and arrested the two suspects in the CVS.

Pesky telephone pole

As for the suspect who took off in the vehicle, officials said a county sheriff's officer saw him and that the suspect crashed the vehicle into a telephone pole. After fleeing on foot, officials said the sheriff's officer was able to apprehend him.

A computer check revealed the vehicle had been carjacked in a nearby county earlier in the day, officials said, adding that a loaded semi-automatic handgun with an extended ammunition magazine, ski masks, and gloves were recovered.

Alonzo Lamont Gholston, 18, Blake Joshua Isiah McKinney, 18, and Barry Tyson, 17 — all from Washington, D.C. — were charged with armed robbery, first-degree assault, second-degree assault, and other related charges in connection with the Dec. 6 incident, officials said.

The sheriff's office told TheBlaze that Gholston fled in the vehicle.

Alonzo Lamont GholstonImage source: Charles County Sheriff's Office

Blake Joshua Isiah McKinneyImage source: Charles County Sheriff's Office

Officials added that Tyson was charged as an adult.

Barry TysonImage source: Charles County Sheriff's Office

(H/T: Blue Lives Matter)