Paddock unleashed a hail of bullets from the 32nd floor of the Mandalay Bay Hotel and Casino that killed at least 59 people in what is now the deadliest mass shooting in U.S. history.
Investigators said they found a box of ammunition in Paddock's hotel room that had 55-year-old Douglas Haig's contact information on it.
Haig told investigators he was unclear if he had met Paddock, but then searched through his records, and recalled that he had met him at the Phoenix gun show Sept. 9.
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Paddock wanted to buy ammunition in bulk that day, but the show was about to close, so they exchanged contact information, according to Haig. Officials said Paddock made a purchase at Haig's home on Sept. 19 of more than 600 rounds of tracer ammunition of various calibers.
Haig said Paddock went back to his car to retrieve gloves before handling the boxes of ammunition that he had just purchased in the weeks before the attack.
What we know about Las Vegas mass shooting gunman
Haig did not have a license to manufacture or sell armor-piercing ammunition, according to authorities. Documents seized during an investigative search of Haig's home revealed more than 100 instances of Haig selling armor-piercing ammunition throughout the country.