-- A city teen faces charges and another teenager was being sought for their roles in

that was recorded in a video widely shared on social media, authorities said Saturday night.

The video shows one teen, who was 17 years old at the time, punch an elderly man in the face as he was about to cross Rosa Parks Boulevard, from Van Houten Street on Dec. 7, according to Paterson Police Director Jerry Speziale.

The attacker faces charges of aggravated assault and endangering an injured victim, the police director said. He was at large.

The other boy, a 16-year-old, recorded the brutal attack and was heard on the video egging on the attacker, Speziale added.

That boy turned himself in to city police at 5 p.m. Saturday to face charges of aggravated assault and endangering an injured victim, according to police.

Speziale said detectives received "countless" tips to help identify the teen in the online video.

"This shameless act of violence was thoroughly investigated and the tireless efforts by the detectives involved is commendable," the police director added in a statement. "The juvenile at large will continue to be sought with the same tenacity and will face swift and decisive justice for this senseless act of violence."

The names of the teens were not released because of their ages. Police asked anyone with information to call investigators.

Detectives Charlie Garcia, Joel Santiago, Mike Figueroa, Cindy Carrera and Jeff Robinson were commended for their work on the case.

State Sen. Tom Kean called the attack "beyond disturbing" in a Twitter message. The senator introduced a bill in Dec. 2013 to "to criminalize the recording, sharing, distribution and publishing of assaults" related to the "knockout game."

The so-called "knockout game" often involve videos of an attacker punching an unsuspecting victim.

Noah Cohen may be reached at ncohen@njadvancemedia.com. Follow him on Twitter @noahyc. Find NJ.com on Facebook.