A concert was marred by tragedy when one reveller died, nine men were stabbed and two others assaulted.
Detectives have not yet identified the victim, who is believed to have died from a suspected drugs overdose at the Swedish House Mafia in the Phoenix Park in Dublin.
Elsewhere three of the men injured in a knife attack remains in a serious condition in hospital.
A 23-year-old suspect was arrested over a number, but not all, of the stabbings at the open-air gig.
Denis Desmond, managing director of MCD Productions which promoted the gig, said every possible precaution had been taken to ensure the safety and security of the crowd.
"Despite our best efforts - with security and gardai personnel levels well in excess of the required numbers for a licensed event of this size - there is only so much one can do to combat anti-social behaviour," he said.
Some 45,000 fans filled the venue for the gig, which featured Snoop Dog, Tinie Tempah, Calvin Harris and headlined with the electronic dance music group, Swedish House Mafia.
A Garda spokesman said a man in his 20s became ill and looked for medical attention from staff at about 7pm.
He was rushed to Connolly Hospital Blanchardstown where he was later pronounced dead.
"Gardai have not been able to identify this man and are asking family and friends to check that loved ones have arrived home safely from the event," a Garda added.
A total of 11 people were assaulted during the night, including nine stabbings.
All aged in their late teens or 20s, were stabbed between 8.30pm and 1am. Several were attacked by the same person.
"A number of the victims required treatment at Connolly Hospital Blanchardstown and three people continue to be treated at the hospital," he continued.
It is understood one of the men in his mid-20s was stabbed several times in the back.
About 30 people were arrested during the evening for minor public order and drugs offences.
Mr Desmond continued: "Obviously we are very disappointed that an individual or very small number of individuals engaged in anti-social behaviour, attempting to spoil the enjoyment of others.
"Such behaviour is certainly not reflective of the vast majority of the 45,000 fans who were extremely well behaved and should be congratulated.
"Unfortunately, anti-social behaviour has become more and more part of daily society with no town or village across the country escaping such conduct."
The city centre park has hosted a series of concerts this week, including the Stone Roses on Thursday and Snow Patrol and Florence & The Machine tonight.
Mr Desmond said as event promoters, MCD work extremely closely with gardai and fully support their tactical operations in combating anti-social behaviour. "Public safety is always our number one priority and we actively engage in detailed planning in advance to ensure this," he added.
Elsewhere Irish Justice Minister Alan Shatter was called on to address the rising violence and anti-social behaviour in the capital.
Opposition justice spokesperson, Fianna Fail's Dara Calleary, said the rise in the number of instances of violent crime in recent weeks was alarming.
"Just last night, seven people were stabbed at a concert in the Phoenix Park," he said.
"To have seven concert goers stabbed in the space of a few hours is absolutely appalling.
"There has been a very worrying trend emerging in Dublin in recent weeks of violent crime being perpetrated on innocent people, in many instances unprovoked and random."