FLAGSTAFF, Ariz. - A Flagstaff police officer was shown on camera Wednesday punching a woman in the face during an arrest.

The officer and another man who appeared to be a police officer were attempting to arrest the woman when the camera started rolling.

She told them multiple times that they did not have a warrant for her arrest and she struggled with them as they tried to handcuff her.

Then the officer punched her.

People who were watching the arrest yelled at the officer before they were able to arrest the woman and put her in the back of a police car.

The Flagstaff Police Department sent a release to media later Wednesday night saying it was beginning an internal investigation into the incident immediately.

"Our agency is very concerned by what is depicted in this video," a release from Sgt. Cory Runge read.

Flagstaff police chief Kevin Treadway said Thursday he was "concerned" with what he sees in the video.