A teenager murdered a fellow teen in a "senseless" knife attack at a party which was advertised on Facebook, a court has heard.
Jay Whiston, 17, was stabbed on the night of September 8 2012, and died in hospital shortly afterwards.
Edward Redman, 18, denies murder.
The "unprovoked" stabbing was described as a "desperate example of the catastrophe and heartbreak" brought about by the use of knives, by prosecutor Mark Milliken-Smith QC during the opening of the trial at Chelmsford Crown Court.
"This is a case about the senseless and tragic taking of a young life so full of promise," he told the jury.
Mr Milliken-Smith said the party where the stabbing took place was "advertised to friends via Facebook and by personal word of mouth" by the host.
The court heard that "numbers grew", and some people, whose presence may not necessarily have been wanted at the party, were in attendance.
"Some of those who attended the party came from a distance and in groups," the jury was told.
Mr Milliken-Smith said Mr Whiston arrived at about 8.30pm with a friend, adding that in the period leading up to the violence the party seemed to have various groups that "weren't really mingling".
Around 100 people were at the party, he added.
The jury heard that Redman and his group brought "an air of unease and tension", and that they were "spreading an air of fear".
They were slightly older than most of the people there and had been drinking earlier in the evening, the court heard.
Mr Milliken-Smith described how an incident broke out when one man was asked for his drink "with a tone", down an alleyway near the house at Marlowe Way, Clacton, Essex.
Redman, of Halstead Road, Colchester, pushed the man who fell back and at this stage Redman punched him, it is alleged.
The man then handed the drink to Redman, and Mr Milliken-Smith said it would appear that Mr Whiston then stepped in and said: "We don't want trouble."
The prosecutor added: "Redman clearly did."
Mr Whiston, of Aster Close, Clacton, was punched and then stabbed and, as he staggered away, Redman followed him, the court heard.
The jury was told Redman then said: "I'm going to do him."
A bottle struck Mr Whiston's head, and Redman stabbed him on his torso, before stabbing him again, the jury was told.
A 999 call was made by neighbours and a trauma team was waiting at hospital, but he was pronounced dead at 10.57pm, Mr Milliken-Smith said.
Redman, by now wearing no top and "realising exactly what he'd done" ran and fled, the prosecutor added.
Later that night, a taxi driver who was booked by Redman said that in the back seat he was "constantly receiving calls or texting".
The jury was told that at one stage Redman said into his phone: "Just tell them there was a big fight. You don't know anything about it."
The taxi driver also said he heard "something about blood".
Redman was taking the taxi to his girlfriend Shannon Fenlon's house, the court heard.
Fenlon, 19, from Jameson Road, Clacton, is on trial accused of perverting the course of justice.
Redman's father, Gary Redman, 51, and brother John Redman, 19, are also on trial accused of the same charge, and all three deny the charge.
A post-mortem showed that the fatal blow killing Mr Whiston was a stab wound to his heart.
The three defendants accused of perverting the course of justice made a concerted effort to ensure that any significant evidence linking Redman to the murder was destroyed, the jury was told.
Redman's phone has never been recovered.
The court heard that Redman went to his girlfriend's house immediately after the party to "distance himself from what he had done and to distance himself from the police".
Mr Milliken-Smith told the jury that when Redman's mother went to collect him the next day he told her he had been in a fight with "pushing and shoving".
Redman's mother noticed he was not wearing the same clothing he had been wearing, and noticed a "bonfire smell" when he got into the car, jurors were told.
Mr Milliken-Smith said that after the incident "social media was understandably abuzz".
The jury was told that via messaging, Redman was asked by someone if he stabbed Mr Whiston, to which he replied: "Yeah, I did."
When asked why he carried out such an act, the jury heard that he replied: "I didn't mean to."
Mr Milliken-Smith said Redman then claimed a fight broke out because they were all drunk.
The jury was told about how Redman went to a girl's house after she was visited by police and said he wanted to know what she told them.
Mr Milliken-Smith said he was, at least in part, "creating an air of intimidation", should anyone say anything against him.
The prosecutor told the court that Fenlon was at a different party that night, and said that when she got off the phone from Redman at one point friends said she had "gone completely white".
She told them her boyfriend had been in a fight and was in trouble and needed to get out of Colchester, the court heard.
Addressing the jury, Mr Milliken-Smith said: "You all need to ask yourselves how he knew there was a stabbing."
The jury are going on a site visit tomorrow and the court will not sit on Friday.
The trial is expected to last up to 10 weeks.