Paramedics took Buffalo Bills NFL Star Damar Hamlin to hospital after he collapsed during a game with the Cincinnati Bengals.
A police escort accompanied the ambulance as it left the Paycor Stadium in Cincinnati, Ohio.
The 24-year-old safety for the Bills collided with the Bengals' receiver Tee Higgins before collapsing.
Hamlin received on-field medical treatment for 30 minutes before being escorted from the pitch and taken to hospital.
The Bills later confirmed that Hamlin suffered a cardiac arrest after Higgins' helmet hit him in the chest.
The team tweeted: "Damar Hamlin suffered a cardiac arrest following a hit in our game versus the Bengals."
"His heartbeat was restored on the field and he was transferred to the UC Medical Center for further testing and treatment."
"He is currently sedated and listed in critical condition."
The NFL rarely suspend games but immediately stopped and postponed the game after the incident.