A 40-year-old man has sadly died following an incident outside Sainsbury's supermarket in John McAdam Way, off Sedlescombe Road North, St Leonards.
Police were called to the store at 9.45pm on Tuesday (2 July). Despite attempts by police and paramedics to resuscitate the man, he was pronounced dead at the scene.
Three men, aged 28, 24 and 53, who were arrested on suspicion of manslaughter have now been released under investigation.
Detective Chief Inspector Alex Geldart from the Surrey and Sussex Major Crime Team said: "This is a tragic incident and our thoughts are with the man's family and friends at this time.
"We would like to hear from anyone who was in the store or just outside the entrance on Tuesday evening at about 9.30pm who may have witnessed something which could help with our investigation."
Witnesses to what happened, and anyone with relevant mobile phone footage of the incident, are asked to contact police online or phone 101, quoting Operation Millbank.
The Independent Office for Police Conduct (IOPC) is carrying out an independent investigation into the death after a mandatory referral was made by Sussex Police Professional Standards Department due to attendance of police to the incident.