Hamlin, a defender on the play, took a hit squarely in his chest. He rose from the tackle and then immediately fell backwards, limp. At least one doctor on Youtube stated that the blow sent Hamlin into cardiac arrest.
The complete lack of body control as he pitches backward is reminiscent of the late Hank Gathers’ collpase on the court during a college basketball game and the late Reggie Lewis’ collapse during a Boston “Celtics” game. Both had pre-existing heart conditions.