Armed police were called to Queen's Park Rangers' Loftus Road ground in west London and 11 men were arrested after Gianni Paladini and an unnamed woman were threatened with the weapon.
After threatening to kill them, the men tried to leave the ground without firing any shots. Metropolitan Police firearms officers managed to arrest some of the men inside the ground, while the rest were detained near the stadium.
"Hammersmith police have launched an investigation following an incident at the QPR football ground today," a police spokeswoman said.
"At approximately 1500 hours, police were called to reports that a number of men had threatened a man and a woman with threats to kill and then left the premises. No one was injured and no shots were fired."
Mr Paladini bought his stake in QPR back in May 2004 and a large proportion of the club is now owned by a Monaco-based group of investors for whom Mr Paladini is the public face.
He lives in London with his English wife, Olga, and has a business portfolio which includes several nightclubs.
Before becoming a director of QPR, Mr Paladini was a football agent who represented a number of high-profile footballers over the past two decades, including the Italian striker Fabrizio Ravanelli, who enjoyed a successful spell in England in the 1990s with Middlesbrough.
QPR won their match against Sheffield United 2-1 to rise to second place in the Coca-Cola Championship.
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