The NFL postponed Monday's game between the Buffalo Bills and Cincinnati Bengals after Bills safety Damar Hamlin collapsed on the field in the first quarter.
The NFL said Hamlin is in critical condition at a local hospital.
A representative for Hamlin, Jordon Rooney, tweeted an update after Hamlin was taken to the hospital: "His vitals are back to normal and they have put him to sleep to put a breathing tube down his throat. They are currently running tests."
There has been no indication when or if the game will resume. Paul Dehner Jr. of The Athletic reported the Bills would return home rather than stay in Cincinnati.
The game was paused at the 5:58 mark of the opening frame, with players heading toward their respective locker rooms.
Hamlin tackled Tee Higgins on a 13-yard reception by the Bengals receiver. He returned to his feet before collapsing. Trainers and medical personnel quickly tended to the 24-year-old.
The magnitude of the situation was immediately apparent upon seeing the reaction from Hamlin's peers on the field.
"Multiple Bills players were visibly distressed and comforting each other as he was cared for by athletic trainers," ESPN's Alaina Getzenberg. "Many players turned away from watching Hamlin in distress."
It initially appeared as though the game would carry on. Per Ryan Miller of the Rochester Democrat and Chronicle, the game officials indicated the players would have five minutes to warm up before action resumed. However, Bills head coach Sean McDermott and Bengals head coach Zac Taylor indicated they wouldn't send their players back out onto the field.
NFL Executive Vice President of Football Operations Troy Vincent later told reporters there was never any suggestion of resuming play.
There was another lengthy delay while the game was temporarily suspended before the NFL decided to call it for the night.
The Bills entered Week 17 at 12-3 and second in the AFC, with the Bengals one game behind in third at 11-4.