The Formula 1 paddock in Austin is mourning the news from Austria about the death of Red Bull founder Dietrich Mateschitz.
Austria's richest billionaire, and the owner of two Formula 1 teams, has died after a long period of illness.
"Apparently it was pancreatic cancer," revealed Roger Benoit, the veteran Swiss journalist for Blick newspaper.
World champion Max Verstappen, who credited his F1 career to the late 78-year-old, led the tributes.
"I was lucky to be able to see him again a few weeks ago and spend some time with him," said the Dutchman.
"The last time I saw him, the things we discussed, that made the day very special even then. And now that final encounter has gained even more depth.
"The news of his death is very difficult to take. I will remember him as a man of gentle character who took care of people with extreme love. He didn't seek the limelight.
"I got to know him as a racer at heart with an enormous passion for the sport. I mean, who else in the history of Formula 1 has ever started two teams?" Verstappen added.
Sebastian Vettel, Red Bull's former quadruple world champion, admitted to being "in shock" about the news.
"I think he was someone who was very special who always managed to do what others didn't think was even possible," he said.
"I don't feel able to share any more memories of him at this time. This is really bad news and I want to think about it first."
Dr Helmut Marko, arguably the closest person to Mateschitz in F1, said his friend and long-time colleague would have wanted Red Bull and everyone else in the paddock to keep charging towards victory in Austin.
"We knew that Didi had a very serious health condition," he said. "But still, now that it has happened, it is incomprehensible to all of us that such a great personality had to step down so soon.
"But in acknowledgment of all his ideas, of all that he has created, we keep going. That's what he wanted.
"All of this in Formula 1 is due to Didi alone. His vision, his trust in the team but also his other entrepreneurial activities, just reflects a truly unique personality.
"But once again, he was a modest person so with this in mind we now want to go into the rest of this weekend calmly but with emphatic results," Marko added.
Finally, even arch Red Bull rival and fellow Austrian Toto Wolff admitted his sadness at the news from Austria.
"Mateschitz was the most incredible entrepreneur," he said. "And not only for what he managed to build for his own product or a great brand, but also for what he did for the sport.
"There was a lot of respect despite all the fighting on the track, so it's also a sad day for Austria and for everyone involved in the sport.
"He did so much, in all kinds of sports - football, ice hockey, all the action sports. And here in Formula 1, I think he was the most groundbreaking entrepreneur and part of Formula 1 history."
