Montgomery County police say they are investigating after a video posted on social media showed an officer using the bottom part of his leg to force a man’s head into the ground during an arrest.

The incident occurred at the Aspen Hill Shopping Center, though neither the video nor a police statement on Twitter specified what day it happened. Police also did not say why the man was detained. The video appeared on social media on Thursday, July 4.

“We are aware of the video that was posted on Twitter regarding the use of force during an arrest by officers from the Montgomery County Police,” the agency’s statement said, noting the department has identified the officers involved. “We have initiated an investigation into the incident and are in the process of gathering all available information regarding the facts and circumstances of this event.”

Authorities did not provide additional information. Spokesmen for the police department and for County Executive Marc Elrich (D) did not return calls seeking comment Thursday night.

The 45-second video shows a group of officers standing around a man who appears to be handcuffed and lying face down on the pavement. One officer leans over him with both hands on the man’s back; the man in custody is screaming profanity.

At one point, the man lifts his head, and the officer uses his shin to force it back down. He then keeps his leg on the man’s neck before lifting the man’s head by pulling on his hair. The video shows the officer forcing the front of the man’s shirt over his face.

Montgomery County Council member Will Jawando (D-At Large), who has focused on police conduct issues since taking office in December, said in a statement posted on Facebook that he felt “alarmed and upset” by the video.

“It’s hard to imagine what circumstances would prompt the officer to use that level of force with a suspect who is already on the ground and restrained,” the statement said.

Jawando said he spoke to the acting police chief, who told him he has asked county prosecutors to “assess if criminal charges are warranted” against the officer. A spokeswoman for Jawando confirmed the council member’s statement.

Montgomery police are also investigating an incident from May, in which police detained a group of young African American men in White Oak and a white officer was captured on video using the n-word while speaking to them in a demeaning way.

The men were given citations for trespassing.