In a brief statement today, the military police said Col. Fabio Almeida de Souza has been replaced.
It didn't provide the reason for Souza's dismissal, but news reports say he is suspected of participating in a WhatsApp chat among officers in which they allegedly praised Nazism.
He's also suspected of allegedly defending the use of violence against protesters during the demonstrations that swept Brazil in 2013.
G1 internet portal cites Rio state's top security official, Jose Mariano Beltrame, as saying he was "horrified" by the messages in the chat and is seeking a police investigation into Souza.