The video begins with the ranger putting up his hands defensively and speaking to the skateboarders. After wrestling the ranger to the ground, the attacker continues to beat him, kicking him in the legs and head and spitting on him. Other skateboarders, all young men, stood by, watching and laughing.
One of them videotaped the beating while a third taunted the ranger, police said.
"It was really disgraceful," said Mariano Verrico of Essex Fells, N.J., who made the video that was posted online and who also promptly turned it over to police.
Verrico said he did not know the skateboarders. He was visiting family in Philadelphia for the day and went to LOVE Park to eat a cheesesteak when he saw the skateboarders begin a verbal confrontation with the ranger. He pulled out his cellphone and began to record the encounter.
Detectives were working Sunday to identify the young men. Verrico's video shows one of them picking up the ranger's hat from the ground and handing it to him before skateboarding away to the other side of the park.
The ranger suffered minor injuries, police said.
Police arrived after the skateboarders left, Verrico said. He accompanied the ranger to the police station to make a statement and hand over his video.
The attack was condemned by the Mayor's Office.
"Park rangers serve an important public purpose, helping visitors and residents in our terrific park system, and it's unfortunate that people engage in violence," said Mark McDonald, spokesman for Mayor Nutter. "And we certainly hope that our employee recovers quickly and that the criminal justice system deals with the individual who did this."