Seven-time F-1 racing champion Michael Schumacher, who retired for the second time last year, was skiing with his son in the French Alpine resort town of Meribel when he fell and hit his head on a rock. Schumacher had been wearing a helmet, but it did not sufficiently protect him.
"Someone who had suffered this accident without a helmet would not have made it this far," said Dr. Jean-Francois Payen, chief anesthesiologist at Grenoble University Hospital Center in France.
The 44-year-old German driver immediately underwent surgery for a brain hemorrhage after arriving at Grenoble already in a coma.
Schumacher, who lives in Switzerland, is being kept company by his wife, Corinna Betsh, and two children, Gina-Maria and Mick.
Doctors say they are taking his injury "hour by hour" and refused to predict the outcome, NBC News reports.
"We cannot predict the future for Michael Schumacher," said Payen. "It's too soon to talk about."
Fellow drivers took to social media to send their well wishes to Schumacher and his family.
Rachel Zarrell is a news editor for BuzzFeed News and is based in New York.
Contact Rachel Zarrell at firstname.lastname@example.org.
Got a confidential tip? Submit it here.