Don Miller, the man at the center of an FBI artifacts raid in Indiana, has died. http://t.co/CJNdf7MeAR pic.twitter.com/e1Fw3fpEnC — IndyStar (@indystar) March 26, 2015

"When I first went into his house and saw the size of the collection, it was unlike anything we'd ever seen," Carpenter told CBS News. "Roughly half of the collection was Native American and the other half of the collection was from every corner of the globe."

Miller knew he had broken laws to obtain his collection, Carpenter confirmed. The elderly adventurer admitted to FBI agents that he'd conducted digging expeditions on both U.S. and foreign soil over the years in violation of antiquities laws.

We’re hanging out at the @MuseumofNature’s Research and Collections Facility open house today showcasing two mammoth tusks that were repatriated to Canada from the United States earlier this year after being recovered during an investigation by the @FBI. pic.twitter.com/YMnFvbHL2h — U.S. Embassy Ottawa (@usembassyottawa) October 13, 2018

The tusks were acquired by American collector Don Miller during a 1960 trip between Calgary and the Yukon border with Alaska, after which he transported the tusks across the border to his home in Indiana. pic.twitter.com/TQldMRHWw0 — U.S. Embassy Ottawa (@usembassyottawa) October 13, 2018

Miller agreed to let agents seize 5,000 of his artifacts so they could be returned to their countries of origin, Carpenter said. The agents collecting the items were shocked when they stumbled upon human remains in Miller’s collection.

"About 2,000 human bones," Carpenter said. "To the best of our knowledge right now, those 2,000 bones represent about 500 human beings.

“It’s very staggering.”

The majority of the bones were dug up from ancient Native American burial sites, Carpenter told CBS News.

Holly Cusack-McVeigh, an archaeology professor brought in on the case, said the looting of burial sites “comes down to a basic human right.”

"We have to think about the context of: Who has been the target of grave robbing for centuries? Whose ancestors have been collected for hobby?" Cusack-McVeigh told the network. "And this comes down to racism. They aren't digging white graves."

Experts have determined the remains are likely those of members of the Arikara tribe, which, according to the online Encyclopedia Britannica, lived along the Missouri River in what is currently North Dakota and South Dakota.

Arikara tribal official Pete Coffey told CBS News he is working with FBI agents to bring them home to North Dakota.

"All too often here we have been treated as curiosities rather than a people here," Coffey told the network. "They could very well be my own great, great, great, great grandfather, or grandmother, you know, that had been -- I characterize it as being ripped out of the earth, you know."