Murder squad detectives have released a shocking CCTV image showing a man pleading for help after being fatally stabbed.
Mark Corcoran, 26, staggered into a convenience store in South Norwood, south London, after being attacked in the street on Valentine's Day.
He collapsed and died from a single stab wound, despite the efforts of paramedics, hours after attending a friend's wedding.
Detective Chief Inspector Cliff Lyons, who is leading the inquiry, said he urgently wants to identify others who were in the shop at the time.
Police want to trace three people caught on CCTV, including a blonde woman who purchased goods less than a minute before Mr Corcoran arrived.
Mr Lyons said: "We would really like to hear from the people in these CCTV stills or from anyone who may know how we can contact them. They are not suspects in this investigation but they may hold valuable information in helping us solve this crime."
Labourer Mr Corcoran, of Croydon, walked into the Subitha Food and Wine shop, in Whitehorse Lane, on Sunday at about 8.20pm. Investigators are trying to retrace his last movements on the street outside the shop to find the knifeman.
They released two CCTV images. The first shows a blonde woman in her twenties at the counter 44 seconds before Mr Corcoran entered the shop. The second shows Mr Corcoran, in a stripy sweatshirt, seconds before he collapsed on the shop floor. Police want to trace other customers in the image.
A man in his forties arrested on Tuesday has been released on bail until the middle of next month.
If anyone has information or may know the witnesses featured in the CCTV images, they should call police on 020 8721 4961 or Crimestoppers on 0800 555 111.