Police say 26-year-old Paul A. Cojocaru of National Park, New Jersey confessed to the attack, and is now charged with Aggravated Assault and Terroristic Threats.
His bail was set at $50,000 full cash. Cojocaru posted bail and was released pending court hearings.
The video that led to Cojocaru's arrest immediately went viral after it was posted online last week.
VIDEO: Violent viral video sparks outrage on social media
In the video, a man is seen beating a 17-year-old boy to a pulp.
After the video was posted, the phones at the West Deptford Police Department began ringing off the hook.
"It took me back. I was very, very shocked to watch what appears to be a juvenile just getting assaulted for no reason at all," said West Deptford Township Police Chief Samuel DiSimone.
Cojocaru's attorney, Vincent Villamor, tells Action News his client is a fitness enthusiast, not a MMA fighter. He also says Cojocaru "is very remorseful."
In a statement Villamor says Cojocaru "was overreacting to somethings that happened at a 3am party," and that it wasn't until "immediately after the incident, he realized what he'd done was wrong."
Police say the beaten teenager is OK, and is not related to the apparent assailant.
"They do know each other so we've made certain that they're not gonna see each other, they're not gonna come together, have any interaction between the two," said DiSimone.
On their Facebook page, police are urging people not to take matters into their own hands, and to refrain from posting any threats on social media or otherwise.
They want to assure everyone the juvenile is safe and is no longer in any danger.