UPDATE: All the men in the video have been identified. Two were arrested and charged with attempted murder. More details released.

ATLANTIC CITY — Authorities released video from a security camera showing men they believed were involved in the shooting of a police officer outside a casino early Saturday morning.

The video is posted above, showing two groups of three men walking toward the camera. One of the men in the second group wears a dark sweatshirt with the words "Atlantic City" on the front while the other two wear baseball caps.

A city officer was critically injured after he was shot in the head. Police returned fire, killing one of the suspects. The rest of the men fled on foot and remained at large Saturday afternoon.

The group of men were near Ceasar's casino about 2:34 a.m. when two uniformed city cops got out of their car to approach them, Atlantic County Acting Prosecutor Diane Ruberton said.

One of the officers was shot as he got out of the car.

The suspects fled in separate directions, Ruberton said. The suspect who was fatally shot was found dead 1½ blocks away on Missouri and Pacific avenues, she said.

Ruberton said police believed the men were "engaged in criminal activity," although she did not elaborate.

The injured officer underwent surgery and remains in critical condition. The officer has not been identified.

Ruberton said her office is being assisted by the State Police, FBI and police departments in Pleasantville, Galloway, and Hammonton.

The NJ Cop Shot Reward program posted a $20,000 reward for information leading to the arrest and conviction of the suspects. “Our hearts are heavy at this hour, but our resolve to captured these suspects remains undeterred,” New Jersey State PBA President Patrick Colligan said

The shooting was the latest incident in a violent week in the Atlantic City area, which included a slaying of a store manager Thursday afternoon at a busy shopping district and a shootout along miles of highway earlier in the week.

Dan Alexander contributed to this report.

Sergio Bichao is deputy digital editor at New Jersey 101.5. Send him news tips: Call 609-438-1015 or email sergio.bichao@townsquaremedia.com.