Coach Gene Chizik opened his postgame news conference by announcing Bagwell died "shortly before the game."
Chizik said he had "a very heavy heart for myself and a lot of our players." He said Bagwell's sudden death was "tragic."
An Auburn spokesman said the 23-year-old Bagwell was from Huntsville, Ala. Bagwell was in his first season as a student coach after working as a student trainer in 2011.
Chizik provided no details on the cause of Bagwell's death but said "our thoughts and prayers go out to his family."