A mid-Missouri police officer has been fired for what his chief says was excessive force against a man in a holding cell.Columbia Police Chief Ken Burton announced the firing Wednesday without naming the officer. But patrol officer Rob Sanders later issued a statement saying he had been cleared by an internal investigation and would fight his dismissal through the appeal process.The firing resulted from an Aug. 15 incident, shown on surveillance video, in which an officer shoved a man against the concrete wall of a holding cell. The man hit his head, and blood can be seen on the officer's arm.Burton says two other officers were investigated for failing to seek adequate medical care for the man, but neither has been placed on leave.