Surveillance video from September 12 shows Sgt. Thomas O'Grady boarding a bus. O'Grady had been riding a bicycle downtown and said Mendoza's bus almost hit him.
Mendoza told investigators the sergeant punched him unconscious. Two police officers were on the bus. According to prosecutors, witnesses say Sergeant O'Grady yelled at Mendoza but didn't touch him.
The video also showed no contact.