According to the Friday report in daily Bild sourced to “high-ranking security officials,” the biker intervened when the four teens appeared to be about to attack the second man who had attempted to flee. The suspected Bandidos member reportedly showed the youths a weapon he was carrying and they backed off.
A spokesman for the Berlin prosecutor's office, Martin Steltner, would not confirm the information about a weapon. But he did say investigators were trying to track down the man as a crucial witness in the case.
“The youths were apparently intimidated by his appearance and ran away,” he said.
The condition of the assault victim, a 30-year-old house painter, is still critical. A spokesman at the Berlin hospital where he is being treated said on Friday that he was in an artificial coma and that a prognosis about his recovery would have to wait until Monday.
The brutal attack, which took place in the U-Bahn station in Berlin's Lichtenberg district late last Friday, was carried out by four male teenagers. The three 17 year-olds and one 14 year-old are in police custody and are likely to be charged with attempted murder and causing grievous bodily harm.
Investigators have lamented the inaction of some witnesses. They say that while several people saw the attack, only one person put in an emergency call. It is thought that one witness might have even stolen the victim's jacket as he lay unconscious on the platform.
The victims' rights group Weißer Ring has called on the federal government to launch a campaign urging people to show more civil courage and not merely look away during such incidents.
“Prizes and commendations for courageous action evidently aren't enough,” said the organisation's spokesman Helmut K. Rüster. “Something has to change in people minds so that they don't just look away when they see violence.”
He warned that people should not become inured to violence in everyday life.