Essex Police have taken the "unusual step" of issuing the names and photographs of Jack Hummerstone, 18, from London, and Andre Vella, 19, from Frinton-on-Sea, and are urging anyone who knows anything about their whereabouts to contact police immediately.
Thomas Brittain, 26, from Essex, died after he was assaulted in the home of a friend, in a flat in Parkside Quarter, Colchester, at around 1.45am on Saturday.
He suffered multiple stab wounds and the provisional result from the post-mortem examination carried out is that he died from a stab wound to the chest.
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The terror attack carried out by Khalid Masood at Westminster that left four people dead lasted less than two minutes say police.
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
The family of the police officer who was murdered in the Westminster attack have thanked those who were with him 'in his last moments'.