A disgraced former Oxford City director has been jailed for more than 12 years for masterminding a $6.6m investment fraud.

City fans branded Thomas Guerriero a "fantasist" and said it marked the end of a "horrible chapter" in the club's 134-year history.

The Sun Sentinel today reported that the court had heard Guerriero - who resigned from his role at Oxford City Football Club in December due to 'ill-health' - splashed his ill-gotten millions on his then-wife and his mistress, fancy homes and exotic cars, and threatened violence against anyone who crossed him.

Guerriero appeared at Miami Federal Court yesterday where Judge Beth Bloom jailed the 39-year-old for 12 years and seven months for destroying the lives of more than 150 people.

Former volunteer at Marsh Lane-based Oxford City, Rob Padbury, said it marked the end of a "horrible chapter" in the club's history.

The 29-year-old ran the club's website for four years and has been a fan for more than two decades.

He said: "I feel the fans' first opinions of him have been justified.

"From day one we knew he was a fantasist but no one quite realised the extent.

"It's a horrible chapter in the club's history and takes away all the great things it does in the community but the most important thing is he no longer has anything to do with the club."

Guerriero - who arrived at the club in April 2013 - came under investigation by the FBI and the United States Securities and Exchange Commission a year later.

He was then arrested and charged in December last year with fraud and conspiracy to commit fraud.

The charges related to dealings by Florida-based Oxford City Football Club Inc, a company owned by Mr Guerriero, which took on a 49 per cent share of the National League South.

He pleaded guilty to conspiring to commit mail and wire fraud in February.

The court heard Guerriero claimed his company owned $90 million worth of real estate, the Oxford City Football Club team in Texas and an online university with 10,000 students that would bring in as much as $100 million and then threatened investors who wanted to back out.

Many of the 150 victims were elderly and particularly vulnerable and some lost their life savings in the fraud, which operated from 2013 to 2015.

Prosecutors Roger Cruz and Rebecca Ryan wrote in court records that Guerriero said to one victim he would "decapitate him, his mother, and his child."

US District Judge Beth Bloom said to Guerriero: "You've destroyed lives, sir" as she imposed a sentence more severe than the 10 years recommended by the prosecution.

Oxford City Stars director James Schall said the ice hockey club, who train at the Ice Rink in Oxpens, met with Guerriero in 2012 but decided to steer well clear.

He said Guerriero subsequently made a bid for the club which was rejected.

He said: "We did meet with him shortly after he arrived at Oxford City but we quickly realised he was not someone that we should be working with.

"The things he was saying just didn't check out, for example he said he had planning permission for an arena in Oxford and that he paid for the club's indoor facility.

"We went back to him and said thanks but we are not interested."

Oxford City Football Club refused to respond to a request for a comment.