Detectives investigating the murder of Chris Foster on Borough High Street on Friday night have released more information about the tragic sequence of events in the hope that it will prompt witnesses to come forward.
Police believe that 34-year-old Mr Foster was stabbed while having a cigarette with a male friend in an alleyway outside St Christopher's Inn at about 11.45pm on Friday night.
He was taken to hospital where he died in the early hours of Saturday.
A post-mortem examination on Sunday gave the cause of Mr Foster's death as a single stab wound to the back.
Witnesses have told police they saw seven suspects wearing hooded clothing carrying baseball bats and at least one knife.
DCI John Sandlin said: "At this stage of our investigation, we believe this to be a case of mistaken identity.
"Mr Foster was stabbed as he stood halfway down the alleyway with his back to the suspects.
"Five of the suspects then carried on down the alley and were involved in an separate altercation with another male, who managed to get away, and his friend. The male friend received a hand injury but did not require hospital treatment.
"I would ask anyone with information about the suspects or any witnesses to please come forward."
The remaining two suspects made off separately.
Anyone with information that may assist the investigation should call the incident room on 020 8345 3865. To remain anonymous call Crimestoppers on 0800 555 111.
A 32-year-old woman was arrested on Sunday on suspicion of assisting an offender. She was taken to an east London police station and subsequently bailed until a date in early February pending further inquiries.