BALTIMORE — The driver of a Baltimore school bus involved in a deadly crash this week should not have been at the wheel because his commercial driver’s license was suspended.

Glenn R. Chappell’s one-year Medical Examiner’s Certificate expired Aug. 31, and the Maryland Motor Vehicle Administration did not receive an updated one, as required by federal law for holders of commercial driver’s licenses, spokesman Chuck Brown said.

Brown provided copies of two warning letters the agency sent Chappell. One, dated July 17, reminded him that his certificate would soon expire. The other, dated Sept. 8, told Chappell, “you are no longer authorized to operate a commercial motor vehicle.” He was told to either submit updated information or have his permit downgraded to a noncommercial driver’s license.

Chappell also could have been kept from driving because he pleaded guilty in 2012 to second-degree assault. A state regulation says a school system “may not” permit someone convicted of a violent crime to operate a school vehicle.