"I have concluded that there is absolutely no evidence to support filing criminal charges against either of the Allentown police officers involved in this incident," Lehigh County District Attorney James Martin said in statement Friday.

Police had launched an investigation earlier this week after a video of the July 11 incident posted on social media appeared to show an officer kneeling on a man's neck while a second officer and another person hold the man's hands behind his back.

The district attorney also looked at a nine-minute, 39-second video shot from a camera across the street from where the incident happened, the statement said.

Officers were at the emergency room of a hospital when they saw a man vomiting and staggering in the street before stopping in the driveway of the emergency room, police had said.

The man began pointing aggressively toward a hospital security officer who was walking toward him with a vomit bag, the district attorney said on Friday.

The officers concluded that the man's "actions were aggressive, and they determined that they needed to detain him for his own safety as well as for the safety of themselves and others, including medical personnel," the district attorney said.

When they attempted to detain him and take him inside the hospital, the prosecutor said, the man resisted and began pulling away.

"In attempting to handcuff [the man], one of the officers placed his knee on [his head] (not on his neck). The officer's knee remained in that position for about 8 seconds and was removed as soon as he was handcuffed," Martin said.

They were able to restrain the man but the officer had to "very briefly" apply his knee to the man's head again because he was spitting on the officers, Martin added.

The man was treated and released from the hospital the following day, police and the district attorney said.

He was identified by the district attorney but CNN is not naming him.

"I am satisfied that given [his] obvious intoxication and his actions, he was clearly a danger to himself and potentially to others," Martin said. "He was clearly agitated and non-compliant, and in order to gain control of him so that he was no longer a danger, and could be medically treated, it was necessary for the officers to restrain him. That restraint was reasonable."

Video shows an officer's knee on man's neck for about 8 seconds

The video that appeared on social media, posted to Black Lives Matter of the Lehigh Valley by a person who asked CNN to remain anonymous, begins with someone driving up on the scene which appears to be outside a hospital.

A person in scrubs is seen observing the incident, and it appears another individual in scrubs is assisting with the person on the ground.

As the man is on the ground with his hands behind his back, one officer places his elbow and then his knee on the man's neck.

It's unclear what led to the video being recorded and what happened after the video. It appears the officer's