Weis didn't identify the sergeant and wouldn't reveal their gender or any details about the officer in question. He also would not say at what district or even in what part of the city the abuse took place.
He would only say that the incident happened this week and that he learned of it earlier Friday and took immediate action.
"This conduct, if true, is inexcusable and is completely out of the line with the standard of professionalism with which our department members are expected to conduct themselves," he said.
The Independent Police Review Authority is investigating, but said it would be "irresponsible to discuss an ongoing investigation" and refused to answer questions.