PORTLAND – Two brothers charged in the fatal shooting of a New Hampshire man at a visitor information center in Yarmouth pleaded guilty Monday in federal court to three firearms charges.

Shawn Hopkins, 28, and Ryan Hopkins, 23, are awaiting trial in state court for the murder of Julius Petrovic, 60, of Bretton Woods, N.H. Petrovic was shot in broad daylight through the window of his parked sport utility vehicle in the information center parking lot on May 17, 2004.

Besides being charged with murder, the brothers were also indicted by a federal grand jury for possession of a sawed-off shotgun, possession of a firearm by a felon and possession of a firearm by an illegal drug addict, said Assistant U.S. Attorney Toby Dilworth.

The federal charges resulted from the discovery of a shotgun that had been illegally shortened when the brothers were arrested five days after the shooting.

Sawed-off shotguns are not prohibited under Maine law, but it is a federal crime to have a shotgun that is shorter than 26 inches or with a barrel shorter than 18 inches. The Hopkins’ gun had a 121/2-inch barrel and was just under 18 inches overall.

The brothers, dressed in orange jail uniforms, entered guilty pleas to those charges Monday before U.S. District Judge D. Brock Hornby. Each count carries a maximum sentence of 10 years in prison and a $250,000 fine, Dilworth said.

They will be sentenced later.

Ryan Hopkins told his estranged wife and two others before his arrest that he was the triggerman in the shooting, according to a state police affidavit. Petrovic was targeted because the brothers, who were arranging a drug deal, thought he had money, the affidavit said.

Even though Ryan Hopkins was the alleged gunman, both he and his brother were charged with murder. Their murder trial is set to begin in July.

Petrovic lived in New Hampshire and worked at hotels from Maine to Florida. He worked for more than a decade as the maitre d’ at the Spruce Point Inn in Boothbay Harbor.