The mother of a 17-year-old boy stabbed to death outside a house party said her son was trying to protect a friend when he was attacked.
About 100 teenagers were at the party in an affluent area of Colchester, Essex, last night.
It is believed the party was advertised on Facebook, but that more people turned up than were invited.
A-level student Jay Whiston, of Clacton, Essex, was taken to Colchester General Hospital with abdominal injuries but died shortly after his arrival, having been stabbed at around 10pm. A provisional post-mortem examination showed he died from a stab wound.
Three teenagers have been arrested on suspicion of murder and are being questioned by police.
Jay, who studied law and business studies at Tendring Technology College, planned to go to university next year.
Detectives from Essex Police said every teenager at the party in Marlowe Way was a potential key witness.
A 17-year-old boy and two 18-year-old men, all from Colchester, are being questioned at separate police stations in north Essex.
A number of homes were sealed off today as police searched for clues.
Empty bottles of vodka and cans of lager could be seen strewn across the front gardens of properties in the street.
Daybreak's chief correspondent Richard Gaisford reports.