He can be seen in the film Original Sins and also played a Civil War soldier in the Denzel Washington film Glory.
The director Eric B. Borgman cast him to play the library director Mr. Hollender over the telephone without even asking him to audition.
"He had this great voice; very powerful and I knew he'd be perfect," said Borgman.
Apart from the character Howard Fisk, Mathis has one of the largest roles in the film.