Detectives are searching for two men after a 37-year-old French chef was stabbed to death following an open-air music concert featuring The Royal Philharmonic Concert Orchestra.
Reynald Duchene, of South Woodham Ferrers, Essex, became involved in an "altercation" with a group of men and women in Southend, Essex, late on Saturday, police said. Detectives said they wanted to speak to two men in the group seen having a "confrontation" with Mr Duchene. They said one of the men was dressed all in white.
Mr Duchene had been watching the Concert in the Park in Priory Park, Southend, with partner Paula Haddlesey, her teenage children and friends, and was attacked in a nearby street shortly after leaving.
Police said one member of the party was thought to have seen part of the altercation and members of the group found Mr Duchene collapsed in a street, police said.
A senior officer said Mr Duchene may not have initially realised that he had been stabbed - and members of the public may have seen the altercation and not realised how serious it was.
Police said search teams had found a knife and detectives were trying to establish whether it was the murder weapon. Detectives said men and women involved in the altercation with Mr Duchene were "possibly of Mediterranean background".
A spokeswoman said one of the men seen confronting Mr Duchene was 20, about 5ft 10in, had a tanned complexion and was dressed all in white.
"He was slim with short, dark spiky hair," said the spokeswoman. "His clothing was three-quarter length white trousers and a white top with a large Nike tick logo."
The second man was of "similar size and complexion", she added.
"We're still trying to clarify the exact sequence of events," said Detective Chief Inspector Godfrey O'Toole, who is heading the inquiry. "We're asking anyone who was in the vicinity of Priory Crescent and Victoria Avenue at this time to contact us. They could be crucial witnesses."