The victim, who is from the Clacton area, has not yet been named by police.
However, tributes began flooding onto the social networking site Twitter using the hashtag #RIPJay.
One Twitter user, under the name Mary-Ellen1, said:
RIP Jay my little brother, taken too young. We will get you justice.
RIPJay, the mark you left on this Earth is irreplaceable, the mark you left in our hearts is unforgettable.
More top news
The London Marathon brings together thousands of people raising money for charity - not to mention some rather unusual costumes.
At least 2,000 people took to the streets of Baltimore yesterday to demand answers over the death in custody of Freddie Gray
Planning on going to the London Marathon tomorrow? Read our handy guide first!