A Newark police officer is under investigation for allegedly assaulting a man during an arrest.

The incident was recorded on video, which begins with a verbal fight between the men. The unnamed officer then appears to punch the man, bringing him down to the ground. The officer then appears to repeatedly punch the man in the face.

It was not clear what sparked the altercation.

Newark Mayor Ras Baraka has called the incident “troubling.”

“As mayor, I will see that this situation is fully investigated,” Baraka wrote on Twitter. “Our police force has been working hard to improve community relations and build trust to the point that our citizen complaints have decreased significantly – and we want to say on that path.”

The mayor says that the officer has been relieved of his gun and has been reassigned.