From [HERE] Video of a white Allentown police officer with his knee on a Black man's neck and neck as two other white cops hold him down drew outrage Sunday from protesters and criticism from officials. The white officer uses his knee to press the black man’s face into the street, up against the curb. The cop then uses his elbow, leaning into his face and neck. Then he switches position again and puts his knee back on the man’s neck/head pressing it into the asphalt. The Black man is handcuffed.

The 39-second clip, shot outside a hospital in Allentown, north of Philadelphia, doesn't show what prompted the confrontation, but three officers can be seen restraining a man lying face down on the ground and yelling.

The Lehigh County district attorney is investigating, a statement said. "Although significant, the entirety of the interaction is being reviewed," the statement said, adding that witnesses were being interviewed and that other videos were being reviewed.

The clip was posted to Facebook and reposted by Black Lives Matter to Lehigh Valley, which demanded that police release body camera video and suspend the officer during the investigation.

Allentown police said in a statement Sunday that the encounter occurred Saturday night after officers saw a man staggering in the street and throwing up. He eventually stopped outside a hospital emergency room, police said.

The man, who wasn't identified, began to yell and spit at officers and hospital staff after they "interacted" with him, the statement said.

The man became noncompliant with police, prompting a hospital staff member to put a spit shield on his head and officers to restrain him, the statement said. It didn't mention the officer's knee on the man's neck. He was released from the hospital later; police didn't say whether he had been arrested.

Protesters gathered outside the police department Saturday night holding Black Lives Matter signs and chanting "defund the police." Video posted by Black Lives Matter to Lehigh Valley appeared to show Allentown Mayor Ray O'Connell talking with protesters outside the police building.