BRIDGEPORT, Conn. – The owner of a gun shop that legally sold a rifle to the Newtown school gunman’s mother pleaded guilty Thursday to unrelated federal firearms violations.

David Laguercia, 56, pleaded guilty in Bridgeport to transfer of a firearm before completing a background check and failure to maintain firearms records, the U.S. Attorney’s office said.

Prosecutors say an investigation found about 300 examples of false or misleading information in Riverview Gun Sales records.

The investigation also revealed at least two instances in which individuals received firearms before getting approval from the national criminal background check system, federal prosecutors said.

“This investigation of one of Connecticut’s largest gun dealers revealed hundreds of record-keeping violations, improper sales, shoddy inventory procedures and seemingly non-existent store security,” said Acting U.S. Attorney Deirdre Daly.

The charges were not related to Nancy Lanza’s purchase. The Associated Press has reported that Lanza bought a Bushmaster rifle from Riverview that was used in the December shooting by her son. Adam Lanza killed his mother at their home, then killed 20 first-graders and six educators at Sandy Hook Elementary School before killing himself.

Laguercia is to be sentenced Nov. 14. He faces up to one year in prison on each of the charges. He also entered a guilty plea on behalf of Riverview to one count of making false entries in dealer’s records. Riverview’s firearms license was revoked Dec. 20.