On 26 October 1993, two gunmen posing as council workers sprayed the yard at Kennedy Way with around 60 shots, killing 28-year-old Mark Rodgers and 54-year-old James Cameron as well as injuring five others.
It was one of a number of atrocities carried out in the wake of the Shankill bomb - when an IRA bomber killed nine innocent civilians and himself in the blast at a fish shop.
James Cameron's wife worked in the Royal Victoria Hospital and had helped victims of the Shankill bomb three days earlier.
Relatives and friends as well as workers, some of whom had witnessed the shooting, laid wreaths during a memorial service at the council depot on Friday.
Colm Cameron was 12 years old when his father James was killed.
He said the family were "reliving 20 years today, we're reliving the pain. It is bad today as it was 20 years ago."
"I feel that the boys in this yard, the city council and the local community will never forget this tragedy that happened 20 years ago. I fell that it should never have happened. It happened for nothing," he said.
Connie Rodgers, described the murders of her brother and his colleague as a "waste of life".
"The people in this yard who came back to work, they've had to live with this as well," she said.
"Today is very important as much for our family and Mr Cameron's family, it's very important for the people that work here and were injured here."
In the 20 years since the shooting, their family has kept and cherished a note sent to them from a Shankill survivor.
It reads: "The slaughter was not carried out in my name, nor in the name of thousands like me. I deeply grieve the tragedy and I extend my sympathy and prayers to the broken hearted.
"May God guide you through your sorrow and give you strength to endure the awful pain. May he guide all of us to learn how to respect each other."