WEBSTER, N.Y. (CBSNewYork/AP) — Police say a 24-year-old woman has been charged in connection with the ambush slaying of two volunteer firefighters responding to a house fire in upstate New York.

New York State Police Senior Investigator James Newell says Dawn Nguyen, of Rochester, faces a state charge of filing a falsified business record.

He says the 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.

Spengler left a suicide note indicating he wanted to burn down the neighborhood and “do what I like doing best, killing people.”

Many questions had been raised about where and how Spengler, who spent 17 years in prison for manslaughter, got hold of the weapons he used in his ambush.

“Spengler had armed himself heavily,” Webster Police Chief Gerald Pickering said. Pickering said Spengler “was equipped to go to war.”

William Spengler mugshot (credit: Monroe County Sheriff's Department)

William Spengler mugshot (credit: Monroe County Sheriff’s Department)

Newell says Nguyen also faces federal charges. A press conference is scheduled for 4 p.m. Friday.

Reached at home before her arrest, Nguyen told The Associated Press she did not want to talk about Spengler.

(TM and © Copyright 2012 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2012 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)

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