A teenager was stabbed to death at a Halloween party in Halifax during a "nightmarish outbreak of serious violence" between rival groups of young men, jurors heard.
Jamie Brown, 17, suffered a fatal stab wound to the stomach in the street outside the party in East Park Road, Lee Mount, Halifax.
A murder trial was told how violence erupted when a group of men from Huddersfield travelled to the party but were refused entry.
Leeds Crown Court was shown mobile phone footage of the moment the teenager suffered the knife wound as the groups clashed.
A 17-year-old male, who cannot be identified, is on trial accused of murder.
Three other youths are also facing serious charges relating the incident on October 27 last year.
Nicholas Lumley, QC, prosecuting, told jurors how the murder accused and his friends armed themselves with weapons including a knife and a hammer before travelling to the party.
He said: "At one of many Halloween house parties being held across West Yorkshire, there was a nightmarish outbreak of serious violence.
"It resulted in the tragic death of a young man, Jamie Brown, just 17 at the time.
"Fatally stabbed in the street outside the house where he had been a guest, until then enjoying his evening.
"He was murdered by one of a group of other young men who had travelled from Huddersfield to be at the same party; some invited, some uninvited.
"That group's intentions, from the outset, were not purely social."
The prosecutor said the group had turned up at the party "ready for violence."
He continued: "After the fatal stabbing, the violent conduct did not cease.
"It continued through the streets, into shops and takeaways in the area. Weapons being gathered, carried. And used."
Another party-goer also received a stab would to the stomach and was hit on the head with a hammer.
The jury was shown CCTV footage of the defendants boarding a bus at Huddersfield bus station as they made their to the party.
Mr Lumley said they went into a McDonald's in Halifax where people in the restaurant feared one of them was going to carry out a robbery.
They arrived at the party at 9.30pm. The prosecutor said: "On arrival at the party, their entry was refused on the basis that too many of their group had turned up.
"The atmosphere quickly turned hostile and some of the defendants were seen to cover their faces.
"Some produced weapons. Plainly they were armed before they knocked on the door."
Some people inside the party threw bottles and aimed punches at members of the group.
The court was shown footage of the disturbance.
Mr Lumley said it was possible to see the shape of a blade in the murder accused's hand and the weapon "glint" in the reflection of a street lamp before he lunged at Mr Brown.
He added: "The stabbing was on another level in terms of necessary or proportionate violence.
"The stabbing was gratuitous, associated with a desire to make a mark, in more ways than one."
Mr Brown died from a single stab wound to his abdomen which damaged major blood vessels
The jury heard the background to the fatal attack may may have stemmed from a previous occasion when some of the defendants had clashed with with a group outside Lee Mount Club.
During that confrontation one of the defendants was heard to say: "I'm not afraid to shank them."
The murder accused gave a written statement after being arrested in which he admitted being at the scene but denied carrying out the stabbing.
Mr Lumley said the teenager may now claim that he picked up the knife and acted for his own safety.
Another defendant told police when interviewed: "This guy who was murdered, he probably attacked us. It's not like I need feel any remorse for him or anything."
The trial is expected to last up to seven weeks and will resume on Tuesday.
None of the defendants can be named. They include:
A 17-year-old charged with murder and an alternative charge of manslaughter. He also denies wounding with intent, violent disorder and possession of an offensive weapon.
Two other 17-year-old males and a 15-year-old male are charged with violent disorder and possession of an offensive weapon.
Jurors were told a 16-year-old male has already pleaded guilty to wounding with intent and violent disorder in relation to the incident.