Three people have been arrested in Newark, New Jersey, on charges of stripping a young man naked in a street and thrashing him with a belt while filming the incident for an internet video.
Newark mayor Cory Booker said the vicious, humiliating beating, reportedly in response to a debt of less than US$30, "was about human degradation".
Among those arrested were the person stripping, then repeatedly belting the defenceless victim, and another who filmed the assault. The video had more than 40,000 downloads on the internet before being removed by websites.
The assault took place last August and in the background of the video people can be seen walking past.
Booker, a popular mayor in the crime-plagued city, said that apart from the "evil" attack, he was also concerned by the fact that "no police report was made whatsoever".
"This level of inaction means that you are actually a participant in that evil itself," he said.
The fact that the video went viral meant the perpetrators eventually were caught.
"This was never reported. We would never know about it if people who saw that video, did not engage," he said. "It triggered an investigation. It took only four days to get these people apprehended."