The young man was waiting for the S-Bahn at the Jungfernstieg station with a friend, aged 17, when he was approached by one member of the group on Friday evening.
“The four other youths followed, and a short, verbal fight broke out,” Hamburg police said in a statement.
According to police, video footage shows the five-person group then set off for the U2 metro train platform, where they were involved in an altercation with another man wearing blue jeans and a white shirt. Police are urgently looking to contact him as a potential witness.
Following the dispute, the group returned to the S-Bahn platform, where they encountered the 19-year-old man and his friend. A fight broke out and the victim was stabbed in his torso.
Police said the mortally wounded young man and his friend escaped toward the U-Bahn train platform, where the victim collapsed.
“Attempts at resuscitation by paramedics called [to the scene] were unsuccessful,” the police statement read.
Police are searching for five teenagers between the ages of 17 and 18, between 170 and 178 centimetres in height, or between 5'7” and 5'10”, and of slender body type. A police spokesman said extensive high-quality video footage of the incident was available.