The 33-year-old man was assaulted outside Grand Central in Birmingham just before 2am on Saturday.
He died in hospital later the same day.
A 34-year-old man was arrested on suspicion of assault shortly after the incident and has since been released on bail "with strict conditions", West Midlands Police said.
Meanwhile a forensic post mortem will be carried out to establish the cause of the man's death.
The are around Stephenson Street and Navigation Street outside New Street station was cordoned off by police after the violence happened.
Detective Inspector Jim Mahon, from the West Midlands Police homicide unit, said: “Tragically a man has lost his life and we are studying CCTV and speaking to witnesses to establish what led up to the attack.”
Anyone with information who has not spoken to police is asked to contact them on 101 or online quoting log 331 of July 31.