When Mollie Tibbetts' stepmother heard the message, she became physically ill.

The pre-recorded call, sent from a computerized autodialer, or robocall, was sent Tuesday afternoon — a week after Mollie was found dead — to her father's phone.

In it, a white nationalist called Mollie's family members traitors to their race. Her father, Rob Tibbetts, thinks he was among the first to receive the message, which claimed if Mollie could be brought back to life, she would say of immigrants, "Kill them all."

"It was unbelievably painful," Tibbetts said in an exclusive interview with the Des Moines Register, recalling how his wife, Kacey Auston-Tibbetts, reacted. "It was everything that’s dark and wrong in America right now."

More: Rob Tibbetts says daughter would not want to beface ofimmigration debate

Mollie Tibbetts was found dead Aug. 21, her body hidden in a cornfield in rural Poweshiek County, after a month of heightened attention on her disappearance.

Authorities charged farmhand Cristhian Bahena Rivera, 24, with first-degree murder, and said he lived in the United States illegally. He confessed to abducting Mollie while she was on a run the evening of July 18, just outside of her hometown of Brooklyn, officials said in an arrest affidavit.

When Bahena Rivera was arrested, some politicians took the opportunity to use Mollie's killing as a rallying cry for tougher immigration laws. The proliferation of hateful messages about immigrants intensified, and activists in Iowa's Latino community reported an uptick in anti-immigrant rhetoric and vandalism.

The robocall message conveyed views Mollie would have considered "profoundly racist," her father said. He called the FBI; the agency told him there was little they could do, citing free speech.

From Rob Tibbetts: Don't distort Mollie's death to advance racist views

Tibbetts said he only listened to the message because the call appeared to be from a Brooklyn, Iowa, number. He was the lone family member to receive it.

"He singled me out," said Tibbetts, who has a Latina stepdaughter and two Latino grandchildren he said Mollie adored. "It was twisted and grotesque."

He ran an internet search and quickly found where the call originated.

The robocall was paid for by The Road to Power, a group with a website and neo-nazi podcast by the same name, according to a recording of the call. The group's white nationalist podcast has been linked to Scott Rhodes, also known as Scott Platek, a resident of Sandpoint, Idaho.

Rhodes has also been tied to other robocall campaigns and phone calls in Oregon, California, and Charlottesville and Alexandria, Virginia. In many of the cases, the calls used a local area code and prefix followed by a four-digit number associated with neo-nazi rhetoric.

Last week, the Iowa Attorney General’s Office said it was investigating the legality of the calls and alerted the Iowa Civil Rights Commission. While the calls may not be illegal, Lynn Hicks, spokesman for the office, described them as "repulsive."

Hicks advised the public to sign up for the Do Not Call registry and download mobile apps that block robocalls. "Treat this like any other robocall: Ignore it. Hang up."

Iowa Gov. Kim Reynolds expressed similar disgust. “It’s unconscionable that somebody would take and utilize a tragic death like Mollie Tibbetts," she said.

More: Complete coverage of Mollie's disappearance and death

Robocalls are often associated with political campaigns and telemarketers. Complaints typically concern requests for money or personal information, Hicks said.

Extremist groups also use them to inspire fear and bring attention to their messages while remaining semi-anonymous, researchers said.

The Iowa Starting Line blog first reported on the calls about Tibbetts. It is not clear how many Iowans received the calls, but WOI-TV, an ABC affiliate in Des Moines, also reported that it received the call.

After hearing the robocall and watching his daughter’s death used repeatedly to advance a cause she vehemently opposed, Rob Tibbetts said it was “just too much to take.” In a guest column published in the Register, Tibbetts responded to a column from Donald Trump Jr. and pleaded with politicians to leave his daughter's name out of the immigration debate.

"On behalf of my family and Mollie’s memory, I’m imploring you to stop," he wrote.

In an interview with the Register on Saturday, Tibbetts said he was tired of his family being abused. While his daughter can’t speak for herself, he said he could and would.

"Everyone, politicians and pundits alike, are on notice," Rob Tibbetts said. "That kind of nonsense will not go unanswered."

Des Moines Register reporters Robin Opsahl and Linh Ta contributed to this story.