The horrific incident happened in the city of Bayonne in southwestern France.
Five individuals on Saturday night tried to board the bus without tickets or masks.
The wear of the mask is obligatory in any kind of French public transportation according to the officially imposed rules to manage the Coronavirus crises.
The bus driver in his fifties attempted to stop misconducting people from entering and was attacked in response. He was repeatedly punched and hit in the head according to the local Police.
The assaulted driver was unconscious when medics arrived.
On Monday the man was pronounced brain dead.
The five individuals who participated in the attack are currently in the Police custody. No official statement on the indecent has been released yet.