The store manager who sold a rifle to Las Vegas shooter Stephen Paddock said he feels “physically ill” knowing he interacted with the man who would go on to commit the deadliest mass shooting in U.S. history.

Christopher Sullivan, the general manager of Guns & Guitars, said Paddock was a customer of the store for about a year and bought five firearms during that time. Paddock stopped at Guns & Guitars to buy weapons on Sept. 28, the same day police claim he checked into the Mandalay Resort and Casino.

Paddock, 64, fired his weapons at a Las Vegas concert Sunday night, killing 59 people and wounding over 500 more.

Sullivan told CBS News he does not feel guilt over Paddock’s actions.

“We do everything right. We can’t control what someone does once they leave this store,” Sullivan said.

“This morning over coffee I was having a moment in myself thinking. I may have very well been the last person to shake hands with that man,” he added.

Investigators reported Paddock had 23 guns in his hotel room. Twelve of the weapons had bump fire stocks, which are legal devices attached to the back of rifles that allow triggers to slide back and forth more quickly to mimic automatic fire.

Guns & Guitars said they did not sell Paddock automatic firearms, ammunition or bump fire stocks. NBC News reported Tuesday that a different Las Vegas gun store, New Frontier Armory, said Paddock purchased a rifle and shotgun once, but that the weapons were likely not used in the attack.

Law enforcement has been in contact with other gun stores in the Las Vegas area, as well.