King's College student David Gaynor was a contented teenager whose life turned around in a "bad four-hour stretch", mourners heard at his funeral.
Mourners filled Holy Trinity Cathedral in Parnell yesterday afternoon to farewell the 17-year-old, who died in hospital on Saturday after attending his school ball.
His father, business commentator and Herald columnist Brian Gaynor, said his son's death was a "terrible reminder of human frailty and how it can turn badly ... in a few minutes, hours or days".
He spoke of how a shy, retiring child had turned into a high-spirited and kind but irreverent teenager.
David was happy in his life, his school, his many sports, and all the "lovely girls from Diocesan, St Cuthbert's, Epsom Girls, and those other schools".
"Just a bad four-hour stretch on Saturday changed all that ... and has had disastrous consequences.
"We were fortunate to have had him with us for 17 years, seven months, and 16 days."
King's College chaplain the Rev Warner Wilder called for a celebration of David's life, but said it was difficult to ignore the sadness of his young death.
"I'm really upset because we shouldn't be here. It is undoubtedly a tragic loss and waste of a beautiful, beautiful, life.
"The really perplexing thing for me is that the David I knew and loved was so happy-go-lucky, giving and kind. David would never hurt a fly, let alone himself.
"We all make mistakes. David made a mistake, and unfortunately this is one he cannot learn from."
Despite testing the patience of many of his teachers, David was an academic overachiever, and was placed in King's A2 class.
Close friend Simon Hickey mentioned David's sporting excellence - his complete domination of the 50-metre breaststroke event, his player of the year accolade for the under-15 football side, and his unplayable left-arm pace bowling.
Despite the family's request that the occasion be "uplifting", many red-eyed students were inconsolable as they filed out of the church to a solo trumpet recessional.
At the end of the service, 200 King's boys ditched their blazers outside the cathedral and performed an emotion-filled haka for the family.
The school's ball on Saturday was marred by allegations of drug use and heavy drinking. David was placed in a room for intoxicated students at the event.