CAMBRIDGE, Mass. — The mayor of a Massachusetts city is calling a video that shows a police officer punch a black Harvard University student several times while he’s pinned to the ground “disturbing.”

Cambridge Mayor Marc McGovern said in a statement Sunday that the police department has assured him the altercation on the video is being investigated. McGovern said, “Cambridge affirms that Black Lives Matter, but it must be true in practice as well.”

Police say officers were called Friday night after receiving reports of a naked man standing on a traffic island. Police say the man resisted arrest once on the ground and the officer struck the man to gain compliance.

The man, Selorm Ohene, was arrested on charges including disorderly conduct and assault. It’s not clear whether Ohene has an attorney.