WILDWOOD, N.J. -- Police have launched an investigation after video posted online shows an officer punching a woman on a beach in southern New Jersey. Wildwood police said on its Facebook page that 20-year-old Emily Weinman of Philadelphia faces multiple charges, including assaulting a police officer and resisting arrest.

CBS New York reports video of Saturday's incident shows an officer clubbing the woman's head twice as she's down on the sand. Voices are heard yelling "stop resisting," though it's unclear who was talking.

Lexy Hewitt was sitting nearby and recorded the take-down with her phone, the station reported.

Get Breaking News Delivered to Your Inbox

"She started screaming initially. It was almost like blood-curdling," Hewitt said. "The officers were on top of her on the ground and that's when I just decided — there's so much going on everywhere — why not, just in case [record the incident]."

The video does not show what led to the confrontation.

Wildwood Police Chief Robert Regalbuto says he finds the video "alarming" but doesn't want to "rush to any judgment" until the investigation is complete.

Wildwood Mayor Ernie Troiano Jr. tells Philly.com the entire episode was a "shame."