A teenager died from a single stab wound to the heart after being attacked in an alleyway near a pub, police said.
The 18-year-old was assaulted near the Peterboat on High Street, Leigh-on-Sea, and taken to hospital by two people at about 18:00 GMT on Friday.
He died shortly afterwards and Essex Police began a murder investigation.
The force said the attack was being treated as a targeted incident and two men arrested on suspicion of causing grievous bodily harm were in custody.
Det Ch Insp Stuart Truss said: “We are making good progress with our investigation and I would ask anyone considering taking matters into their own hands not to do so, but let us investigate so we can bring people to justice.”
Officers were given additional stop and search powers in the Old Leigh area overnight.
Ch Insps Chris Bradford said: “Any death, especially in such tragic circumstances, will understandably have an effect on the close-knit community and we are aware a vigil has been organised for the young man who died.
“While we understand people wish to pay their respects, we would ask them to please do so in private at home.”
Police said extra officers would remain in the area on Sunday and urged people to speak to them if they saw what happened or had video footage.