Federal prosecutors said the man, Michael Vangpa of Dracut, robbed three convenience stores on Christmas Eve last year.
Vangpa allegedly flashed a gun and demanded cash from the clerks in the three separate robberies, two of which were in Lowell and one in Tewksbury. Prosecutors said the man shot the gun in one of the robberies, and that they all took place within one hour.
Vangpa is charged with two crimes: the first is interference with commerce by robbery, which carries a sentence of up to 20 years in prison and a fine of up to a quarter of a million dollars. The second, discharging a firearm in furtherance of a crime of violence, carries a mandatory sentence of ten years — and up to life in prison.
The man has been in federal custody since August 12.