Mark Madoff (46), the oldest son of disgraced financier Bernard Madoff, was found hanging in his Manhattan apartment at 6.28am local time Saturday (0.28am Sunday NZ time).
It was the second anniversary of Bernie Madoff's arrest for history's largest Ponzi scheme, involving $US65 billion.
Police found Mr Madoff hanging from a dog leash attached to a pipe running across the ceiling.
His two-year-old son was sleeping in a nearby room, as was the family's dog.
No suicide note was found.
Mark London, a lawyer and stepfather of Mr Madoff’s wife Stephanie (who was in Florida), called police at 7.30am.
Mr London had called on the apartment after receiving a call from Mr Madoff asking him to check on the child.
Upset by article
According to a source quoted by The New York Post, Mr Madoff was upset about a front-page report published by The Wall Street Journal today on the aftermath of his father's fraud.
The Journal's series of articles included one headlined Madoff's Kin Eyed as Probe Grinds On, which said Mark Madoff and his brother Andrew faced possible tax fraud charges.
Fresh scrutiny
Mark and Andrew Madoff worked in the trading division of Bernard L Madoff Investment Securities, and were not directly implicated in the massive Ponzi scheme.
At the time of their father's 2008 arrest, neither son was among the eight people charged.
However, The Wall Street Journal reported today that Federal prosecutors were scrutinising the Madoff sons, implying that they could re-visit the decision not to prosecute.
And The New York Times reported that last week Mark Madoff, along with other directors and executives of a Madoff affiliate in London, had been named as a defendant in a civil lawsuit filed by the trustee seeking assets for victims of the scheme seeking $US900 million.
Additionally, on Wednesday US time, Irving Picard, the court-appointed trustee for the liquidation of Bernard L Madoff Investment Securities, named all the directors of the company's London subsidiary in a new lawsuit in an attempt to recoup $80 million.
A separate suit, filed by Mr Picard last year, accused Mark Madoff of using $US66 million he received improperly to buy luxury homes in New York, Massachusetts and Connecticut.
The apartment Mr Madoff was found in today was in an upmarket area and fellow tenants included rock star Jon Bon Jovi.
Claimed ignorance of fraud
By a Vanity Fair account, Mark Madoff was "gregarious", while his brother Andrew was more cerebral and tech savvy.
Both worked for their "strict, secretive" father their entire careers, but claimed ignorance of his wide-ranging fraud.
According to the pair's official account, in December 2008 their father called them to his office and revealed he had been defrauding clients.
Mark and Andrew immediately contacted the US Department of Justice and the Securities and Exchange Commission and Bernie Madoff, who cooperated fully with authorities, was arrested soon after. He is now in jail.
The popular conspiracy theory was that with debts mounting and knowing he would be unable to keep his fraud hidden much longer, Bernie Madoff sacrificed himself to save his sons.
But in today's Wall Street Journal report, the brothers' lawyer, Martin Flumenbaum, reiterated that neither son had any knowledge of the Ponzi scheme prior to their father's December 2008 confession.
After the initial furore of the scandal died down, The Guardian reported, Mark tried unsuccessfully to get a job in trading before starting a company making applications for iPads.
NBR staff
Sun, 12 Dec 2010