(CNN) An Arizona man who says he sold ammunition to the gunman in the 2017 mass shooting in Las Vegas pleaded guilty on Tuesday to federal charges.

Douglas Haig , 57, admitted he manufactured ammunition without a license at a workshop inside his Mesa home, the US Attorney's Office in Nevada said.

Authorities began investigating Haig after they found unfired .308-caliber (7.62mm) rounds in gunman Stephen Paddock's hotel room. Two rounds had Haig's fingerprints on them as well as tool marks from his workshop. The bullets in the cartridges were armor-piercing, with an incendiary capsule in the nose, a criminal complaint said.

Paddock opened fire on October 1, 2017, from his hotel room at the Mandalay Bay hotel onto a crowd attending the Route 9 Harvest music festival. Fifty-eight people were killed and 422 others were wounded. Investigators say Paddock died of an apparent self-inflicted gunshot wound as police closed in on his room.

Haig's charges do not allege that he knew of Paddock's intentions to kill in Las Vegas.

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