Video surveillance of an unprovoked November 2012 attack on an American exchange student in Copenhagen has been released publicly, and it is not a pretty sight. The video shows passengers on a city bus looking the other way as four juveniles kick and punch the victim.

The surveillance video, broadcast this week on TV2's Station 2 programme and available below, shows Nick Townsell, an American of Asian descent, sitting quietly in his seat when the four boys start verbally taunting him and making slant-eyed gestures in his face. One of the boys then kicked Townsell in the stomach, encouraging the rest of the gang to join in with a flurry of kicks and punches.

No-one else on the bus attempts to stop the assault or even seems to acknowledge that the attack is occurring.

“I completely understand that people do not want to physocally interfere in a conflict like this, but they should at least tell the bus driver so he can push his panic alarm,” Mads Helios from the Copenhagen Police told TV2 News. “None of wants to become the next victim, but someone could have called 112.”

Helios said that police have solid leads on the identities of the assailants so they might as well turn themselves in.

“We have some names, so they can count on seeing us soon,” said Helios.

Police have received twenty calls from residents offering the names and schools of the suspects after the TV2 broadcast.

In the video, Townsell at first looks unsure of what is happening when the boys begin to shout insults like “China boy” and other racial slurs at him. He appears to yell for help from his fellow passengers to no avail.

“I do not think it is becoming for Danes not to act when any of our fellow human beings are attacked in this way,” said Helios. “You have an obligation as a citizen to do the right thing.”

Townsell – who returned to the US shortly after the assault – said that he was shocked that no-one came to his aid during the attack, but that he has put it behind him.