WEBSTER, N.Y. – A 24-year-old woman was arrested Friday and charged in connection with the Christmas Eve ambush slaying of two volunteer firefighters responding to a house fire in upstate New York.

Dawn Nguyen of Rochester, N.Y., faces a state charge of filing a falsified business record, State Police Senior Investigator James Sewell said.

Nguyen also faces a federal charge; a news conference with the U.S. attorney in western New York was scheduled for 4 p.m. Friday.

Sewell said the state charge is connected to the purchase of an AR-15 semiautomatic rifle and a 12-gauge shotgun that William Spengler had with him Monday when firefighters Michael Chiapperini and Tomasz Kaczowka were gunned down. Three other people were wounded before the 62-year-old Spengler killed himself.

He also had a .38-caliber revolver, but Nguyen is not connected to that gun, Sewell said.

The .223-caliber Bushmaster rifle, which had a combat-style flash suppressor, is similar to the one used by the gunman who massacred 20 children and six women in a Newtown, Conn., elementary school earlier this month.

Nguyen and her mother, Dawn Welsher, lived next door to Spengler in 2008. On Wednesday and again on Friday, shortly before her arrest, she answered her cellphone and told the Associated Press that she didn’t want to talk about Spengler.

Her brother, Steven Nguyen, told the Democrat and Chronicle newspaper of Rochester that Spengler stole the guns from Dawn Nguyen.

A number listed in the name of her lawyer, David Palmiere, was disconnected.

Spengler set a car on fire and touched off an inferno in his Webster home on a strip of land along the Lake Ontario shore, took up a sniper’s position and opened fire on the first firefighters to arrive at about 5:30 a.m. on Christmas Eve, authorities said. He wounded two other firefighters and an off-duty police officer who was on his way to work.

A Webster police officer who had accompanied the firefighters shot back at Spengler with a rifle in a brief exchange of gunfire before the gunman killed himself.

Spengler spent 17 years in prison for killing his grandmother in 1980 and was barred from possessing weapons as a convicted felon.

Investigators still haven’t released the identity of remains found in William Spengler’s burned house. They have said they believe the remains are those of his 67-year-old sister, Cheryl Spengler, who also lived in the house near Rochester and has been unaccounted for since the killings.

The Spengler siblings had lived in the home with their mother, Arline Spengler, who died in October.

In all, seven houses were destroyed by the flames.

Investigators found a rambling, typed letter laying out Spengler’s intention to destroy his neighborhood and “do what I like doing best, killing people.”

He had been released from parole in 2006 on the manslaughter conviction, and authorities said they had had no encounters with him since.