WASHINGTON – A former neighbor of the Webster, N.Y., sniper who killed two volunteer firemen on Christmas Eve illegally bought the guns used in the killing, federal authorities charged Friday.

Dawn M. Nguyen, 24, of Greece, N.Y., was charged in federal court with acting as a straw purchaser for William Spengler, who as a convicted felon could not legally buy guns for himself. Spengler was convicted of killing his grandmother in 1980. Nguyen also faces state felony charges for allegedly falsifying business records.

U.S. Attorney William J. Hochul Jr. said Nguyen purchased a Bushmaster .223 semi-automatic rifle and a Mossberg 12-gauge shotgun from the Gander Mountain store in Rochester on June 6, 2010. But in truth, he said, she “knowingly made a false statement in connection with the purchase of the two firearms” and actually was acquiring them for Spengler.