"I was really upset, I can't get to sleep over it," Kanti Patel, a Leicester City fan, told AFP as emergency workers pored over the crash site.
There was no confirmation whether 60-year-old billionaire Vichai Srivaddhanaprabha, who frequently flies to and from Leicester's home games by helicopter, was on board the aircraft.
But many in the city in central England and in Vichai's homeland already feared the worst for the man they credit with the club's against-all-odds Premier League title victory in 2016.
"It means a lot to me, he did a lot for the club. To be honest I don't know what to say but I can't get over it. Since him being with the club the club has done well, and I don't know what's going to happen now," Patel said.
A picture shows tributes outside Leicester City Football Club's King Power Stadium in Leicester, eastern England, on October 28, 2018 after a helicopter belonging to the club's Thai chairman Vichai Srivaddhanaprabha crashed outside the stadium the night before. // AFP PHOTO
Another fan, Tom Lievers, arrived with a "Champions" scarf to pay tribute to Vichai.
"Well you know where we were when he bought the club -- we were absolutely nowhere. So I brought down my 'Champions' scarf because he made us champions."
Andrew Aldwinckle said: "He was more like he was a supporter, a proper supporter, rather than a money man. He was one of the crowd. As far as we're concerned, that's it."
Steve Walton, who wore the club's blue hat, said: "I think there's a lot of Leicester fans around the world -- not just in Leicester, but around the world -- who I think will be devastated and he meant a lot to the fans."
Vichai also brought Thailand greater recognition in the international sporting world, developing the Southeast Asian country's football scene.
At a football game in central Bangkok, Leicester City fan Apichart Jitratkavee said: "He is an important person who has raised the bar of Thai football further.
"There were projects by Leicester City to select Thai teenagers to train in the club's academy. They will have a chance to serve the nation in the future."