Federal prosecutors charged an Arizona man with illegally manufacturing and selling armor-piercing bullets in connection with the Las Vegas massacre in October. (Video: Reuters, Photo: Brian Skoloff/AP/Reuters)

Federal prosecutors charged an Arizona man Friday with illegally manufacturing and selling armor-piercing bullets after investigators found some of his ammunition among the belongings of Stephen Paddock, the gunman who shot and killed 58 people at a country music festival in Las Vegas in October.

According to a complaint filed in federal court in Phoenix, Douglas Haig, 55, an aerospace engineer who sells firearms ammunition as a hobby, sold more than 700 rounds of ammunition to Paddock — including armor-piercing bullets that Haig did not have a license to manufacture. Federal investigators concluded that Haig has sold armor-piercing ammunition on at least 100 occasions since July 2016 via his Internet business, including to clients in Nevada, Texas, Virginia, Wyoming and South Carolina.

Authorities said Paddock first met Haig at a gun show in Las Vegas in August and then later at a gun show in Phoenix in early September, when Paddock said he wanted to buy bulk ammunition. Paddock met Haig at his home on Sept. 19 to purchase hundreds of rounds with cash; law enforcement officials found ammunition with Haig’s fingerprints inside Paddock’s hotel room at the Mandalay Bay Resort and Casino after the Oct. 1 shootings, authorities said.

The charging documents do not suggest that Haig knew that Paddock was planning a mass shooting.  Haig appeared in court Friday afternoon and was released on bond. If convicted, he faces up to five years in prison and a $250,000 fine.

Haig and his attorneys could not immediately be reached for comment Friday.

“I had no contribution to what Paddock did,” Haig said during a news conference Friday, during which he said he does not believe any of the ammunition he sold Paddock was used in the mass shooting. “I had no way to see into his mind.”

Court documents released earlier this week showed that in the days after the shooting, investigators considered Haig a person of interest. In an interview with CBS News, Haig said he was contacted by police the day after the attack because investigators found an Amazon box with his address on it inside Paddock’s hotel room.

Haig told CBS that he met Paddock at a gun show last fall and later sold him 720 rounds of “tracer” ammunition — bullets that use a chemical to stream a trail of light when fired. Such ammunition allows shooters to see where their bullets are landing, which can help with targeting, especially at night.

“I couldn’t detect anything wrong with this guy,” Haig told CBS. “He told me exactly what he wanted. I handed him a box with the ammunition in it, and he paid me and he left. … He said he was going to go put on a light show.”

Authorities have not yet found a motive for the Las Vegas massacre. A preliminary 81-page investigatory report about the shooting rampage concluded that Paddock acted alone.

Paddock, 64, who had no prior criminal history, stockpiled weapons in the year before the shooting, ultimately buying 55 rifles and other guns in addition to scopes, cases, bump stocks and large amounts of ammunition, according to the report. But it remains unclear why he targeted the concert, the central mystery that has gone unsolved since he opened fire on the Route 91 Harvest festival in the deadliest mass shooting in modern U.S. history.

Paddock moved guns and ammunition into his hotel suite in the days before the attack, concealing them in luggage and sometimes getting help from the hotel bell desk while using a luggage cart and freight elevator. He set up cameras around the area so he could know when officers were closing in. According to police, Paddock shot a hotel security guard through his door not long before firing at the music festival across the street.

When police officers eventually breached Paddock’s suite, they found him dead from a self-inflicted gunshot wound, a handgun not far from his body.