A 21-year-old Bulgarian suffered no injuries after a gunman opened fire in the shop the boy was working in, located in Denmark's capital city of Copenhagen late on Sunday.
The Bulgarian lay on the ground to evade the bullets.
The shooter escaped and the witness did not manage to precisely describe him.
Police authorities have immediately arrived at the crime scene to arrest several youngsters, who were wearing armed vests but it later emerged they were not involved in the attack.
The shooting came just a few hours after demonstrators staged a protest against the violence in that region of Denmark.