Now 72 and retired, the white-haired Nielsen is a testament to the survival of the fittest on the Great Plains. Whipsawing wheat and cattle prices have cycled beyond many farmers' ability to survive in recent years, enabling Nielsen to add other men's land, feedlots and houses to his oil-and-gas empire to a fortune a former accountant says is worth at least $40 million.

His legacy is still unfolding, as is a small-town drama that divides three generations of family members. The story turns on simmering suspicions over love, money and death — turning Nebraska courts into something of a paper mill — and the fable, however farfetched, of family claims to billions of dollars of stock in investor Warren Buffett's company, Berkshire Hathaway, based in nearby Omaha.

In November, Nielsen's three adult sons filed lawsuits accusing him of defrauding their late mother Barbara of tens of millions of dollars and possibly more in a divorce as she lay dying of cancer more than 15 years ago. Their lawsuits are based primarily on the financial records and testimony of their father's former accountant, Rodney Zwygart, who possesses 32 boxes of their father's business records. He recently agreed to turn over the files.

Zwygart, a bull-shouldered CPA, makes the most sensational allegations against his former client. In October, in his own Chapter 11 bankruptcy proceeding in Lincoln, Zwygart said he helped Nielsen set up a Nevada trust to hide from the Nielsen family 50,000 shares of Berkshire Hathaway Class A stock putatively worth $4.5 billion. The only proof he has provided is a Reno attorney's bill, initialed as paid, for "trust and tax planning." It makes no reference to the stock.

Nielsen and his longtime lawyer, Charles "Ken" Mock, declined to comment for this story. In a deposition in another family lawsuit, in which he admitted temporarily removing funds from his grandchildren's savings accounts, the elder Nielsen roundly defended his business practices and said he owned no Berkshire Hathaway stock. He blamed his sons for the family dispute. "They brought this all on, and I'm going to finish it," he said without elaborating.

Berkshire Hathaway Chairman Buffett, 73, known as "the Oracle of Omaha," says he has "never heard of Donald Nielsen, nor is there any record of his being a significant shareholder," according to a letter he wrote to one of the Nielsen sons' attorneys in January 2003.

The USA's second-richest man declined to comment for this story. But ownership of Berkshire Hathaway's Class A shares — worth $89,300 apiece — is elite company. Management reported only 8,200 shareholders of record as of the latest annual report in March.

Even if the Nielsen sons' dreams of inheriting Berkshire Hathaway billions seem remote, the paths of the elder Nielsen and Buffett occasionally crossed. And many of the family's accusations about Nielsen's supposedly shady dealings and hard-heartedness echo complaints his customers have made in recent years.

USA TODAY interviewed more than 50 Nielsen family members, friends, former employees and business associates who span more than a half-century of the elder Nielsen's life. Almost all of them independently raised serious questions about his conduct. Also, the Cuming County courthouse, in this depressed farm town 70 miles northwest of Omaha, contains numerous records of money disputes between Nielsen and people with whom he did business.

Orin Abendroth, 69, a farmer who lost 53 acres to Nielsen in a disputed bankruptcy proceeding nearly 20 years ago, says of the businessman now, "He just cruises along like he's some kind of giant."

Starting from scratch

Newly married in 1951 to the former Barbara Jean Kephart, Nielsen began his career by pumping gasoline and washing windshields at a Standard Oil service station in Omaha, a few blocks from the house in which Warren Buffett still lives and where Buffett and his wife buy gasoline, station personnel say.

Zwygart says Nielsen told him he would clean Buffett's windshield and talk to him about stocks he was interested in. That way, Nielsen reputedly said, he had an "in" with the investor at the very beginning.

In 1953, the Nielsens moved to West Point, where Buffett's mother, Leila Stahl Buffett, grew up and where her father, John Stahl, was the school superintendent and local newspaper publisher.

Nielsen formed Nielsen Oil and Propane, an independent dealer for Standard Oil of Indiana, part of which later became Amoco and in 2000 merged with British Petroleum as BP.

Meanwhile, Buffett formed his first investment business, Buffett Partnership, in 1956, after he put together a $105,000 grubstake, according to published accounts. "He would stop periodically at the shop in West Point through the years," says Larry Miller, who joined Nielsen Oil in 1964 and still works at the successor company, Sapp Bros.

Buffett's investing prowess was legendary. Forbes estimates his net worth today at $36 billion.

Nielsen also achieved almost unfathomable success on the hardscrabble plains, although on a smaller scale. "There'd already been three (Standard Oil) guys in here that had gone broke. He became the Kansas City (region) leader. That means he was the biggest in six states," recounts the eldest son, Steve Nielsen, 50.

Even as Nielsen prospered, some acquaintances perceived another side of the businessman.

Former Nebraska Highway Patrolman Bill McNutt, who worked for Nielsen part time from 1972 to 1974 and full time from 1979 to 1984, says Nielsen often replaced premium fuel with cheap fuel and profited on the difference. "I didn't think it was right," McNutt says. Several former Nielsen Oil employees independently corroborated this account.

Another former employee, Gerald Poppe, who worked at Nielsen Oil from 1970 to 1984, says Nielsen truck drivers, including him, routinely cheated customers by partly offloading their fuel at company facilities yet charging for full tank loads when they served customer accounts.

"They always checked to see if (the tanker) was empty (upon completion)," Poppe says. "But never once did they crawl up to see if it was full when it come." Several people corroborated this account.

Tough business tactics

Cuming County, the state's breadbasket, foundered in the late 1970s and early 1980s. Its farmers and ranchers were beset by collapsing commodity prices and rising interest rates that turned even small loans into unpayable debts. Nielsen survived by being tougher than the times, even when offering to help those less fortunate than him.

"He pretended to be your friend, and he wasn't," says Reuben Leimer, 78, who, during a contested bankruptcy proceeding in the mid-'80s, forfeited the 800-acre family farm his grandfather had settled. Nielsen, having supplied Leimer with fuel and fertilizer on credit, ended up owning the farm.

And Nielsen made sure the outraged Leimers did not squat on his former homestead. He ordered his middle son, Mike, to burn and bulldoze the Leimers' house, according to court records and interviews.

Leimer's former daughter-in-law, Patricia, filed an affidavit in related litigation contending that the elder Nielsen physically threatened her and other Leimer family members on at least three occasions.

"He told me, and I quote, that if they seen anybody on the farm, 'They would be shot,' " Patricia Leimer testified. She could not be reached for comment. Her former husband, Glen Leimer, whom the affidavit cites as a witness, said in an interview, "It was something to the effect of: 'If certain people get around here they will be eliminated.' They meant force."

Dealing with death

Barbara Nielsen, a smart, tough brunette, ran the Nielsen Oil office until the breast cancer she was diagnosed with in about 1980 progressed to her bones, family members and friends say. After forays to Greece and Mexico with her husband in search of a cure, Barbara began in the late 1980s to discuss how to prepare her estate, say her three sons, a close friend and Zwygart, the family accountant.

The Nielsens' inability to agree on the estate led to increasingly harsh arguments, according to eyewitnesses. Zwygart says he attended the couple's final negotiation before they filed for divorce.

"I was up in the kitchen, Mrs. Nielsen was in a wheelchair and Don Nielsen was standing there. And Mrs. Nielsen said, 'I want to be able to give my boys $1 million when I die,' " Zwygart said in an interview. According to several accounts, Don Nielsen countered that their sons would receive $1 apiece.

"The last thing (Barbara) said," Zwygart recalls, "she stood up in the wheelchair, and I don't even know how she had the strength — 'You're not going to keep me from doing what I think is right for my kids.' "

The Nielsens' November 1989 divorce decree and property settlement valued the family's net worth at about $1.4 million and divided the holdings in half. Barbara Nielsen was awarded $625,000 in cash, the house and its furnishings, although the court permitted Don Nielsen to live in the basement, which he boarded off, say family and friends.

Zwygart says Barbara Nielsen's divorce attorney, now deceased, never asked him for a financial statement or even spoke with him. One record Zwygart recently provided to the Nielsen sons is a financial statement he prepared for Don Nielsen's bank, First National Bank of Beemer, that conservatively pegged his assets at $5.3 million when he was telling the divorce court he was worth less than one-third of that.

A year after the divorce, Zwygart prepared another financial statement for Nielsen and his new wife, Sarah, based largely on Nielsen's own assessments. It pegged his half of the fortune at $17.5 million while citing many of the same assets in the previous financial statement, the accountant's records show.

Among the big changes: Don Nielsen went from being overdrawn at the bank by $400,137 to having $543,095 in cash. Shares of Standard Oil (by then renamed Amoco), which he accounted for in 1989 as $159,731 "at cost" now were valued at $1.6 million "at market." Land he had valued at less than $1 million now was valued at nearly $6 million. Buildings formerly stated at $1.1 million now were stated at $3.5 million. And Nielsen Oil, the company he and his first wife founded and which he previously valued at $779,000, was listed at $4.5 million.

The Nielsen sons say they were suspicious of their father even then but were unaware of these confidential business records until a dozen years later when Zwygart provided them with their father's financial statements and tax returns and with a copy of the divorce decree, which the court had sealed.

Clint Poppe, the Lutheran minister who often attended to Barbara Nielsen at her home, says, "I think this is a classic example of money and power consuming even love for spouse and children and grandchildren, to the point an individual has been blinded to the important things in life." Duane Nielsen, the youngest son, 39, says, "We wish we could put it behind us and move forward. We'd love to have a life with our father. Unfortunately, he's 72 years old now, and it's probably not going to happen."

Even armed with Zwygart's records and testimony, the Nielsen brothers are unsure of winning a judge's permission to reopen the divorce decree and property settlement in the Cuming County courthouse, where their father so often has prevailed. And should they succeed in that unusual maneuver, they also will have to win court approval for a new hearing on Barbara Nielsen's estate, which they argue technically never was closed due to the failure of some of the heirs to pay their estate taxes.

The townsfolk of West Point, an economically ailing alcove on the weather-battered plains, appear numb to the prospect of more pain in the family feud.

Here, where Don Nielsen's bright red pickup is among the few signs of prosperity, his sons — two of whom are unemployed — are no financial match for their father. Their key ally, Zwygart, is likely to see his credibility challenged after the state Board of Accountancy recently revoked his CPA license after hearing a complaint from his former clients and partners in an unrelated business.

In an interview, Zwygart acknowledged he was complicit in the elder Nielsen cheating his former wife and indicated he might be acting now out of revenge as much as contrition. Zwygart told the federal bankruptcy judge in Lincoln — where he first placed some of the Nielsen family's personal records on the public record — that he sought protection from creditors not because he was insolvent but because Nielsen was buying his IOUs from creditors to foreclose on the accountant's assets, a tactic Nielsen used to crush so many other former business partners, the accountant alleges.

Berkshire Hathaway attorney Lori Cleary, who attended one bankruptcy hearing, argued that the Nielsen family feud and the accountant's claims shouldn't encroach upon Buffett or his company's records, arguing that stock transfer archives are "confidential business records that the company simply can't, you know, release to anybody just when they ask."

Buffett stated his own view in the letter he wrote to one of the Nielsen brothers' attorneys last year. "The only thing I can tell you," Buffett wrote, "is that if Donald Nielsen claimed to own 50,000 shares of Berkshire Hathaway stock, he was totally delusional."