A gathering will be held at the Trades Hall building in Wellington on Thursday to mark the 30th anniversary of a bombing of the building.
Caretaker Ernie Abbott was killed in the blast which no one has ever been charged.
Memories of 27 March 1984 remain vivid for those affected by the bombing.
Phil Mansor still vividly remembers the moment - 5.19pm - when Ernie picked up the suitcase bomb and died.
"My first reaction was some bastard has put a bomb at my door," he said.
"I got down there and it was a complete shambles and just looking at Ernie I just didn't do anything. I couldn't move," he said.
Trades Hall Committee chairman Paul Tolich had just left Trades Hall. He also remembers the hall's caretaker well.
"You know it was one of those occasions when you thought of him.
''He was a jolly sort of a bloke. He loved the horses," he said.
Unionist Graeme Clark noticed the green, tattered suitcase as he left the building for a union meeting.
He said he and another union member would've picked up the bag, but had their arms full of leaflets.
Pat Kelly was a prominent unionist at the time of the blast.
His raw emotion was still clear the morning after the bombing.
"That dirty, scabby bastard can do this sort of thing, then we're going to do something about it. But I can't comprehend what's happened at the moment," he said the day after the bombing.
His daughter, Helen Kelly, is now the president of the Council of Trade Unions. She says her father was shaken by the attack.
"Dad was so upset. I've never seen him so inconsolably upset," she said.
In the days afterwards, inquiry head Ted Lines, said his team of 100 officers were determined to catch the bomber.
"A man is dead and we've got a responsibility. We should apprehend that person," he said.
Detective Inspector Mike Arnerich was a young detective at the time of the bombing. He says information still comes to the police from time to time, but they can go without any new information for five or six years.
For the 30th anniversary, a service will be held at the Trades Hall and there will be a minute's silence at at 5.19pm.