By Alex Tresniowski
January 10, 2011 12:00 PM

Once, it had been a wonderful thing to be a son of the brilliant Bernie Madoff. But after Dec. 11, 2008, when Madoff was arrested for running the biggest Ponzi scheme in history, that blessing became, for his boys Mark and Andrew, a terrible burden. Andrew, who had run his father’s trading floor along with Mark, quickly moved away from finance, going fly-fishing and starting a new life. But Mark, 46, the more sensitive son, could not let go; instead, he hoped he could still succeed in business. “He was trying to get back into the financial world, and who in that world would ever take him on with his last name?” says a close friend. “It doesn’t make sense. It was almost as if he were blind.”

Mark Madoff’s struggle to deal with the scandal ended abruptly on Dec. 11, 2010, two years to the day after his father’s arrest. At 4:00 a.m. he wrote an anguished e-mail to his vacationing wife to have someone come to their Manhattan apartment to “take care of Nick,” their 2-year-old son. Then he slipped a cord around his neck, tied it to a ceiling beam and hung himself as Nick slept in a nearby room. To many who knew him as a handsome, charming man, the suicide was both shocking and yet not entirely a surprise, given the turmoil in his life since he and his brother turned their father in to federal authorities for bilking investors in a $65 billion scam. And, far from providing answers, his death has only deepened the mystery surrounding his role in the swindle: Were Mark and Andrew just as guilty as their father, or were they victims too? And if Mark was innocent, what drove him to such a desperate act? “Mark was in a really dark place, and he just saw no way out,” says a source who worked for Bernie Madoff for many years. “The whole world believed he did these monstrous things, and he thought his family would be better off without him.”

While Bernie, 72, was sentenced to 150 years in prison, Mark and his brother have not been charged with any crime. But both were targets of numerous civil lawsuits from victims who accused them of profiting from the scheme. And despite the passage of time, it was clear that things were getting no better for them. Just days before Mark’s death, a new lawsuit named three of his children as defendants; there had also been increased media speculation about whether or not he himself would be charged. In the face of all that, many of the friends and associates interviewed by PEOPLE insist that Mark so idolized his father that he simply couldn’t see what was happening. “He looked up to his dad 100 percent, as almost godlike,” says Allan Klein, a friend who knew Mark since high school. Steve Raaen, a financier and friend for 15 years, says, “His self-identity was as a fortunate person who always strived to do the right thing. So when he was accused of doing the worst thing, that was more than he could bear.”

Growing up in tony Roslyn on the North Shore of New York’s Long Island, Mark “was not snobby; most of us didn’t even know he was rich,” says Brett Cantor Harris, a childhood pal. In high school, adds a former classmate, “He was an all around American kid; he was smart, he played sports, he loved hockey. He was a very genuine, caring guy.” Mark married his college sweetheart Susan, and they had two children. After their divorce in 2000, Mark met Stephanie, a former executive assistant, and married her in 2003. Their two young children, Nicholas and daughter Audrey, were the center of his life, says the source who worked for his father: “Mark was so proud of his kids, and when they started talking or walking, he’d come into the office and tell you about it.”

Mark’s other passion was working for his father. “The family name meant everything to him,” says another close friend. “He and Andrew were the sons of a billionaire, and they could have worked three days a month, but they were always there, every single day.” It was precisely this pride in their father, says the friend, that made the revelations about the Ponzi scheme so staggering to them.

Before long, though, Mark’s shock gave way to anger, say those who knew him. “It was almost like [his father] was dead to him,” says a childhood friend. Even so, when his wife legally changed their children’s names from Madoff to Morgan after his father’s arrest, Mark “wasn’t thrilled they had to do that,” says a close family friend. In 2009 Mark fled from his apartment after he and Stephanie, 36, had a bitter fight; she reported him missing to police, but he turned up after spending a night in a nearby hotel. Despite all the stress, Stephanie “had no intention of leaving Mark,” says the close family friend. “She really loved him, and she was very protective of him.”

Mark also tried hard to salvage a career for himself on Wall Street. While his brother seemed happy to leave finance behind-a lymphoma survivor, Andrew biked 100 miles a week and worked with his fiance at her consulting practice-Mark founded a real estate newsletter, the Sonar Report, hoping to reestablish himself in the business world.

But that never happened. In December, when his wife and daughter were away in Florida, Mark stayed behind in their $6 million apartment in Manhattan’s SoHo neighborhood. There seemed no outward cause for alarm. On Dec. 9-two days before his death-Mark appeared excited about Christmas. “He was having people over on Christmas Eve, and he was looking forward to it,” says the family friend who spoke with him that day, a Thursday. “He sent Stephanie a text saying he couldn’t wait to get a tree on Sunday.” Then on Friday he stopped by his Manhattan parking garage for some chitchat. “He was going to get a bagel, and I said, ‘Get a wheat bagel, they’re good for you,’ and he said, ‘I don’t like the way they taste,’ ” remembers Jay Blatt, owner of the garage. “He was as normal as ever.”

But just a day later, he got up early and wrote a series of disturbing e-mails-“No one wants to hear the truth,” he told his attorney-before hanging himself. His family had him cremated and held a private gathering instead of a funeral. According to reports, Bernie Madoff was stunned by the news and for a time didn’t leave his cell even for meals; Mark’s mother, Ruth, with whom he had not spoken in months, is said to have blamed Bernie for the death. Mark’s wife, Stephanie, “is devastated and terrified of being alone with two little kids,” says the family friend. “She is trying so hard to hold it together for them.”

Mark’s suicide, tragic as it was, will not end the lawsuits; creditors will continue going after his estate, which includes houses in Connecticut and Nantucket. Yet even one of Bernie Madoff’s victims-Adele Fox, 87, a retired secretary who lost her life savings-sees the elements of a Greek tragedy in his death. “The name Madoff became like a curse,” says Fox. “I think Mark was guilty, but if he wasn’t, can you imagine what this did to him? His death is terrible, because it shouldn’t have come to this.”