CEDAR RAPIDS, Iowa (AP) – A retired National Park Service official was sentenced Friday to one year of home detention and 10 weekends in jail for stealing the ancient remains of Native Americans in 1990 and stashing them in his garage for years.

U.S. Magistrate Judge Jon Scoles scolded Thomas Munson, former superintendent of Effigy Mounds National Monument in northeast Iowa, for removing bones tied to more than 40 individuals from the monument’s collection and lying about it for two decades. Scoles said Native American leaders who were denied the ability to rebury their ancestors were “understandably outraged” by the disregard with which Munson handled their bones, which were significantly damaged by the time they were recovered in 2012.

“This is clearly an outrageous criminal act,” Scoles told the 76-year-old, frail Munson in a federal courtroom in Cedar Rapids as representatives from several tribes looked on. “There can be no explanation for what he did.”

The sentence ends a painful case for the National Park Service, which is tasked with preserving the picturesque monument site along the Mississippi River that many tribes consider sacred. The monument includes hundreds of earthen burial and ceremonial mounds, many in the shape of animals, that were built by Native Americans between 700 and 2,500 years ago.

During excavations from the 1950s to the 1970s, scientists dug up bones and skeleton fragments of dozens of individuals who lived and died there. The remains were kept at the monument and considered historically significant.

Munson ordered a subordinate to pack the bones into two cardboard boxes in July 1990, then drove them to his home across the river in Prairie du Chien, Wisconsin. They stayed there for more than two decades but decayed due to inappropriate storage conditions.

Munson told investigators he was concerned about a federal law that took effect in November 1990 requiring museums to transfer remains and any associated burial objects to affiliated tribes. The purpose of the law – the Native American Graves Protection and Repatriation Act – was to allow for reburials consistent with tribal traditions.

But Munson believed the law would allow tribes to make suspect claims that would decimate the monument’s collection of burial objects, which he saw as more valuable than the remains. Once the bones disappeared, tribes could not make claims on the burial objects.

The National Park Service learned soon after Munson’s retirement in 1994 that the remains had vanished. Questioned over the years, Munson denied responsibility and floated several other possibilities for where they went. The monument opened another investigation in 2011 under new superintendent Jim Nepstad, and Munson returned one of the boxes. The next year, a federal agent recovered the second box in Munson’s garage.

“This is absolutely the worst case of racist, bigoted and callous behavior I have ever encountered,” said Patt Murphy, of the Iowa tribe of Kansas and Nebraska, whose inquiry seeking an inventory of the monument’s remains prompted the investigation. He said he spent years working to get his ancestors’ remains from museums and properly reburied, but Munson denied them that opportunity.

Sandra Massey, historic preservation officer for the Sac and Fox Tribe in Oklahoma, said Munson handled the remains like “trash.”

“Those are my people,” she said. “What kind of sick mind does this kind of thing?”

Munson issued a written apology but showed no remorse in court. In a rambling statement, he said “nobody knew what to do with” remains at the time.

“A lot of it was not intentional,” Munson said. His attorney Leon Spies then cut him off, telling Scoles his client has been “experiencing some cognitive difficulties.” Spies said Munson’s theft was an “uncharacteristic act” for a man who worked with tribes for 30 years.

Scoles ordered Munson to pay $108,000 in restitution, the cost of repairing the collection. Once restored, the remains are expected to be returned to tribes.