A Nebraska man says that he is not guilty of illegally selling firearms to people who told him they were felons because the items were out of his personal collection of 678 guns and 13 grenades.

According to documents unsealed in U.S. District Court on Tuesday, 35-year-old Ashley Gerbig is charged with six counts of knowingly selling firearms and ammunition to a confidential informant working with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).

The documents allege that the informant purchased "a Ruger .22 caliber rifle, Valtro 12 gauge tactical shotgun, Sig Sauer .40 caliber pistol, Century International Arms Inc. AK-74 assault-style rifle, Bushmaster AR-15 rifle and Nodak Spud LLC AK-47-type side-folding stock assault rifle" without being required to provide a permit, the Lincoln Journal Star reported.

Last month, ATF agents raided Gerbig's home and seized 678 guns, 13 grenades and various other mortar and tank rounds.

Court records indicated that authorities launched the investigation after an anonymous tipster who bought a gun over the Internet complained that Gerbig told him he didn't need a Federal Firearms License (FFL) to sell guns that he personally owned. The tipster thought it was unusual that Gerbig charged sales tax for personal sales.

Sens. Joe Manchin (D-WV) and Pat Toomey (R-PA) on Wednesday responded to the December mass shooting of 20 elementary school students in Connecticut by announcing a bipartisan bill that would close the so-called gun show loophole and also require background checks on firearms sold over the Internet.

Gerbig allegedly was selling the same type of military-style assault rifles that was used in the Sandy Hook Elementary School massacre.

"Your timing, based upon what's going on in the world and country, is absolutely the worst it could be," Magistrate Judge F.A. Gossett said at March 20 hearing. "Do not violate any condition of this release or, I will guarantee you, you will sit in jail until trial.”

Gerbig faces up to 60 years in prison if convicted on all counts.

The Journal Star reported on Thursday that Gerbig also claimed he did business with members of law enforcement. The ATF said he had applied for a Federal Firearms License, but was rejected for violating the federal Gun Control Act. His father reportedly lost his license in 2010 after also violating the same law.

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