Three people – none of them Jewish – were fatally shot when Miller went on a shooting spree outside a Jewish Community Center and retirement community located in Overland Park, Kan.

John Mark Reidle, 48, of Aurora, Mo., pleaded guilty last month in U.S. District Court to a federal charge of making a false statement in acquisition of a firearm – admitting he bought the Model 870 shotgun Miller used in the April 13, 2014, shooting. Reidle also is believed responsible for supplying Miller with a handgun -- apparently purchased at a gun show -- used in the murders.

Court documents say Reidle confessed to purchasing a Remington shotgun four days before the shooting at a Wal-Mart in Republic, Mo., “on behalf of an acquaintance he identified as Frazier Glenn Miller,” who also is known as Frazier Glenn Cross.

FBI agents located and questioned Reidle about the shotgun purchase a day after the shooting spree. He was indicted on the federal firearms charge in May 2014.

“The defendant acknowledged that he was not truthful when he filled out the ATF Form 4473, in that he knew he was buying the gun on behalf of Frazier Glenn Miller,” court documents say.

A sentencing date has not been set, but Reidle, who remains free on bond, could face up to 10 years in prison.

Reidle apparently shared Miller’s anti-Semitic beliefs and has flown a Nazi flag outside his ramshackle mobile home where he is self-employed as a junk dealer, the Kansas City Star reported.

Miller told Reidle “that he wanted to purchase a shotgun for his son’s birthday, but did not have any identification” to complete the purchase. Because he was a felon, Miller couldn’t legally purchase firearms himself.

A blast from the shotgun claimed the life of William Lewis Corporon, a 69-year-old medical doctor as he was driving into the parking lot of the Jewish center. His 14-year-old grandson, Reat Griffin Underwood, who was in the car, died from handgun wounds. Terri LaManno, 53, of Overland Park, Kan., also died in the shooting spree.

The written plea agreement says it doesn’t prevent Justice Department prosecutors from charging Reidle with murder, attempted murder or conspiracy to commit those crimes. But apparently, at this juncture, prosecutors can’t develop probable cause to prove Reidle had advance knowledge of Miller’s planned shooting spree.

It occurred a month after the life-long racist and former Ku Klux Klan leader learned he was terminally ill with emphysema. He stood trial this past summer in Olathe, Kan., acting as his own attorney, claiming his racist beliefs directed him to target Jews to “save the white race.”

After the six-day trial, it took the same jury panel 90 minutes before deciding the 74-year-old former Army Green Beret and self-described anti-Semite deserved the death penalty for the murders.