A fifth teenager has been arrested on suspicion of murder after a man was stabbed to death.
Essex Police said it believed the man in his 30s was "going to the aid of another man" when he was attacked.
Officers were called to Iris Mews, Laindon, near Basildon, shortly after 21:30 BST on Sunday.
Det Ch Supt Steve Jennings said the man "lost his life during an altercation which ensued with a group of young people not directly known to him".
He described the incident as "a tragic loss of life" and appealed for anyone with information to contact officers on 101.
"A family has been broken apart, and we need to get to the bottom of what happened," he said.
Police said those arrested were three boys and two girls, aged between 13 and 16.
Three of them have been released on police bail until later this month.