BANGOR — One of three people charged in connection with a pair of Rite Aid robberies in Augusta last year pleaded guilty Friday in U.S. District Court.

Dominic J. Pomerleau, 21, of Augusta pleaded guilty to the federal equivalent of robbery and attempted robbery.

Pomerleau, who in December pleaded not guilty to the charges, faces up to 20 years in prison, a $250,000 fine and three years of supervised release on each charge.

Judge John Woodcock Jr. questioned Pomerleau for about 25 minutes to ensure he understood his actions, and was pleading guilty of his own free will.

Pomerleau’s attorney, James Nixon, said there was no sentencing agreement in exchange for the change of plea.

Pomerleau, who has been in jail since his arrest, will continue to be held until sentencing, the date for which has not been set.

Pomerleau, who was on probation at the time, is one of three people charged in connection with the Sept. 2 robberies of Rite Aids on South Belfast Avenue and Hospital Street. The robberies occurred just 20 minutes apart.

Lance M. Szady, 26, of Augusta like Pomerleau, is facing federal charges of robbery and attempted robbery. Szady has already served a state prison sentence for a 2010 pharmacy robbery.

Nichole A. Breton, 20, of Chelsea was charged with being an accessory after the fact in connection with the robberies for allegedly being in the car while the robberies took place and using the stolen oxycodone.

But Breton was not listed in online court documents Friday. It is not clear whether she is still facing federal charges.

Pomerleau was convicted in January 2012 of eluding an officer and sentenced to four years incarceration with all but nine months suspended and two years of probation.

Other documents filed in state court say Pomerleau had that probation revoked several times and had been released after serving six months in jail only four days before the pharmacy robberies.

Documents filed in the federal case indicate that Szady and Breton dropped off Pomerleau at MaineGeneral Medical Center in Augusta the morning after the robberies.

Material filed in Breton’s case said she told investigators the trio spent the evening of the robberies using the stolen pills and cocaine.

“At one point in the night, she and Szady returned to the house to find Pomerleau passed out and foaming at the mouth,” said an affidavit by FBI Special Agent Cameron Mizell, who sought the warrant for Breton’s arrest.

Another document said Pomerleau lay halfway in a closet and was not breathing.

Szady allegedly told investigators he drove Pomerleau to the two Rite Aid locations.

Both he and Breton told investigators that they and Pomerleau had been swimming at Breton’s aunt’s in Augusta and left in Szady’s car, stopping first at McDonald’s on Bangor Street, where she got paper and a pen. Pomerleau then wrote on it, she said.

The first robbery occurred at 5:30 p.m. at the Rite Aid on North Belfast Avenue, where Pomerleau handed the pharmacist a note that read: “I have a gun. Don’t push the button or I’ll shoot,” according to Mizell’s affidavit.

The robber demanded the painkiller oxycodone and Ritalin, which is a brand name for methylphenidate, a stimulant used to treat attention deficit-hyperactivity disorder.

The affidavit did not say whether Pomerleau actually had a gun.

“Hurry,” the note said. “Make it a minute or less. Act normal.”

Mizell wrote that the phone rang as the pharmacist was getting the pills, at which point the robber ran out of the store before getting the pills.

“Witnesses provided a description of the man,” Mizell wrote. “That description included information about distinctive tattoos on the man’s arms and neck.”

Pomerleau has a variety of tattoos, including a large star on his neck, that are clearly visible in a variety of posts on his Facebook page.

About 20 minutes after the first robbery, a man in a different color T-shirt robbed the Rite Aid on Hospital Street.

The man again approached the pharmacy counter with a note that threatened a gun and demanded oxycodone, Mizell wrote.

The robber was given pills and fled the store. Witnesses’ descriptions of the robber, including the distinctive tattoos, matched those provided after the first robbery, Mizell wrote.