A video that shows two Missouri police officers beating a man believed to be mentally ill has sparked a police investigation.

According to St. Louis Public Radio, Mario Crump’s family had called police for assistance on March 21 after they say he began acting erratically.

Footage shows officers striking the man and telling him to put his “motherf***ing” hands behind his back. The individual, who appeared to initially resist the instructions in the video, appears to eventually comply.

Watch the video (editor’s note: vulgar language is used):

It’s not clear, however, what happened before or after the 40-second video, which was shot by a family member.

Mike Keller, the executive director of a center for individuals with mental illness, told the St. Loius Post-Dispatch that Crump ultimately suffered two broken hands, six broken fingers and a head wound that required five staples to close.

“I looked at it and it made me sick,” he said, upon seeing the video.

St. Louis police chief Sam Dotson said he is determined to get to the bottom of the incident.

“Any police department, when things like this happen, we have to ask ourselves, what did we do right, what did we do wrong,” Dotson said, according to St. Louis Public Radio. “Immediately it was very clear to me that there needed to be an investigation internally to try and understand what happened that night.”

Both officers had reportedly taken courses teaching them how to interact with the mentally ill.

“But what I think is important is, this is a block of instruction,” Dotson said. “By no means does it put the officers in the position where they are a psychologist, or a psychiatrist, or even a clinician.”

Follow Oliver Darcy (@oliverdarcy) on Twitter