FORT LAUDERDALE, Fla. -- A former potential investor who reported prominent lawyer Scott Rothstein to the FBI said he was not sure if an investment opportunity he was offered was the "greatest deal around" or a "total fraud."

According to U.S. Customs and Border Protection officials, Rothstein returned to the U.S. via Fort Lauderdale Executive Airport on Tuesday afternoon. Security personnel at Rothstein's mansion said Rothstein and his wife are in South Florida but would not be returning to their home Tuesday evening.

Federal authorities on Monday were conducting a criminal investigation into Rothstein, who is suspected of operating a Ponzi scheme by selling tens of millions of dollars in fabricated legal settlements to investors.

Those close to the case said Rothstein was selling investors something called structured settlements.

"You settle a lawsuit -- let's say a personal injury lawsuit or a discrimination lawsuit -- and they want to pay out over a number of years, but you don't want to wait a bunch of years. So somebody agrees to buy your settlement at a discount for cash so you get money now," said securities attorney Jeff Sonn. "So allegedly, he was selling structured settlements and supposedly investors were funding those settlements and now apparently the investors' money is gone."

Alan Sakowitz said that only a few months ago, he sat on Rothstein's lizard-skin couch and listened to an investment pitch to buy structured settlements.

"We were going to pay $660,000 for each one, and we would get $300,000 a month for three months on each one," Sakowitz said.

But Sakowitz said the numbers just didn't crunch.

"He was a big actor in love with himself, and we weren't sure if it was the greatest deal around or total fraud after our first meeting," Sakowitz said.

Sakowitz said Rothstein told him he settled 3,000 cases a year because he had intimidating people and technology to get companies and individuals to settle lawsuits before they went to court.

“Former police officers, including the former Broward County sheriff, and they had surveillance equipment. They could hear what was going on down the street. They filmed people inside of offices, they went through trash cans," Sakowitz said.

On Sept. 22, Sakowitz called the FBI, but afterward, he feared for his family's safety.

“Scott only cared about himself. When we were talking, he leaned forward … one day and I saw on his ankle a gun there, and I knew he lived a $10 million lifestyle and he wasn’t going to let anybody stop him living that lifestyle, and I wasn't going to find out," Sakowitz said.

Sakowitz said federal investigators told him his information was valuable but never contacted him again.

“If I was wrong, they would find out in one hour, and if I was right they could have saved people tens of millions of dollars," Sakowitz said.

On Tuesday in a Broward County courtroom, Rothstein's partner, Stuart Rosenfeldt asked a judge for control of their law firm's finances.

"He has, in my view, for now, relinquished his authority with regard to that law firm," said Judge Jeffrey Streitfeld.

"It's going to make us stronger eventually. I never realized how much I love the people who have remained and stayed by my side who could have walked away and just left me holding the bag," Rosenfeldt said.

Rosenfeldt went on to say he did receive some text messages from Rothstein Tuesday morning but would not disclose what they said.

Rosenfeldt did receive control of the firm. He said he thinks he can save the lawyers but not the firm.

Local 10 did try to call Rothstein's lawyer several times, but it went straight to voicemail and his inbox was full.

Effects Of Allegations Could Be Far-Reaching

The ripples of Rothstein's alleged pending financial collapse could hit almost every corner of South Florida society, Local 10's Neki Mohan reported. Rothstein is part-owner of the Versace mansion and restaurant in South Beach and Bova Prime on Las Olas Boulevard.

Rothstein paired up with sports superstars like Dwyane Wade and Alonzo Mourning to fundraise around town. He gave away millions to charity.

"The man has a kind heart. There are so many charities -- Dan Marino Foundation, Holy Cross (Hospital), Joe DiMaggio (Children's Hospital). Where it came from, I don't know. I don't want to speculate, but it certainly was a very generous process," said Chip Lamarca of the Broward Republican Party.

According to state records dating back to 2006, Rothstein, his wife and his law firm donated $532,000 to the state Republican Party, $208,900 to Sen. John McCain, $200,000 to state Democrats and $9,600 to Gov. Charlie Crist's Senate bid.

So far, some politicians have said they returned contributions, including state Chief Financial Officer Alex Sink.

"If you are a recipient of money, you have to look very quickly at what you want to do. You want to be ahead of the ethical curve," said Mitch Cesar of the Broward Democratic Party.

Holy Cross Hospital got a $1 million pledge from Rothstein last year and planned to name a lobby in his honor. The hospital would not comment on the scandal and would not confirm whether Rothstein had paid the money but did say the project had not broken ground.

Until now, Rothstein's name was plastered on big business deals and community service. Now, it is also plastered on scandalous headlines.

Local 10 called several charities to which Rothstein has donated, but none of them wanted to comment at this time.