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.
More top news
Russell Davy is still haunted by the memory of Eddie Heath, the chief scout he says sexually assaulted him at Charlton.
A leaked letter has caused huge controversy.
Video taken in Soho Square shows sparks flying into the air as the men cut through a lock on the Ducati bike.