Three teenagers have been arrested on suspicion of murder after a 17-year-old boy was stabbed to death at a house party.
Police said around 100 teenagers were at the party in an affluent area of Colchester when the stabbing happened.
Essex Police said officers were called to reports that Jay Whiston, of Clacton, had been stabbed during a disturbance outside the house in Marlowe Way at around 10pm on Saturday night.
He was taken to Colchester General Hospital with abdominal injuries but died shortly after arriving. Police said a provisional post-mortem examination result showed that Jay died from a stab wound.
A 17-year-old boy and two men, both aged 18, have been arrested on suspicion of murder. They are all from Colchester and are being questioned at separate police stations in north Essex.
Senior investigating officer, DCI Simon Parkes, said: "This really is tragic loss of life that we, but more importantly, this boy's parents have to deal with. This murder took place in an affluent area of Colchester and at a house party which had a garden that could cater for the 100 or so teenagers that were present.
"Although we don't yet know the details of what went on, we're slowly piecing together the sequence of events that led to this boy's death. We're speaking to those who were at the party, but we're mindful that there may have been others who left either before the stabbing or in the immediate aftermath before we arrived.
"Everyone at this party is a key witness whether they saw anything or not and we would urge them to contact us. Our thoughts are very much also with this boy's family. They are being supported by our family liaison officers."
Jay's heartbroken mother Caroline Shearer said her son had been trying to protect a friend when he was stabbed.
Ms Shearer, 46, said: "It's any mother's worst nightmare. He was loved by everyone and so caring. My son had never been in trouble with the police before. He hated bullies and hated people being unfair. I still feel numb but I'm starting to feel angry now. How can thugs ruin innocent lives at their will? There's no rhyme or reason to it."