Austin Box, starting middle linebacker for Oklahoma, died on Thursday at the age of 22.
According to multiple reports, Box was found unresponsive and taken to Mercy Hospital in El Reno. He was transferred to Mercy Hospital in Oklahoma City, where he was pronounced dead.
"The University family is deeply saddened by the tragic death of student-athlete Austin Box. Our hearts go out to his family and friends," school president David Boren said in a statement.
A spokeswoman at the medical examiner's office said that they do not expect a cause of death to be known Thursday.
Box started in five games last season and recorded 37 tackles. He graduated earlier this month.