The Archbishop of Glasgow has revealed that he tried to comfort a woman who had seen her teenage daughter and both her parents "killed almost right in front of her" in the bin lorry tragedy.
Erin McQuade (18) and her grandparents Jack Sweeney (68) and his wife Lorraine (69), all from Dumbarton, were killed in the incident in Glasgow on Monday. Primary school teacher Stephenie Tait (29) from Glasgow, Jacqueline Morton (51) from Glasgow, and Gillian Ewing (52) from Edinburgh also died in George Square.
First Minister Nicola Sturgeon said afterwards that the city had been left with a "broken heart" after the crash while the congregation at a special prayer service were told that Glasgow was now "united in grief".
Ten people were also injured in the accident yesterday. Six of them, including the driver of the bin lorry, are still being treated in Glasgow hospitals. George Square had been sealed off with steel cordons as police investigated the crash.
When those were lifted members of the public who had been touched by the incident went to the scene to leave tributes to the victims, whose bodies were removed by a fleet of private ambulances yesterday morning.
Archbishop Tartaglia told a memorial mass at Glasgow's St Andrew's Cathedral that he spent time with those who had lost their loved ones on Monday evening, just hours after the incident.
He said: "On the evening of the tragedy, I was privileged to be permitted to spend some time with one of the families who had been cruelly devastated by the incident. I was able to witness and share the grief and sadness of a mother and of a father for their daughter, and of two daughters for their mother and father.
"The distressed woman to whom I was speaking had seen her daughter and her own parents killed almost right in front of her. Can you imagine the horror?
"I tried to console them and comfort them. We spoke and we cried and we were silent before the abyss of their loss and the random meaninglessness of what had happened. They openly spoke of their faith, but their faith was sorely tried, and I commended them silently to God that the Lord would find the way to bring them comfort."
The Christmas lights are being turned back on in George Square today, as Glasgow tries to move on from the tragedy, although the winter carnival rides and ice rink will not reopen until noon on Boxing Day.
Archbishop Tartaglia said today's service was taking place "for the victims of the tragic incident" in George Square, which happened just over a year after the Clutha disaster claimed the lives of 10 people when a police helicopter crashed into a crowded pub.
In his sermon the archbishop said: "Just over a year ago, we had the Clutha disaster, and now we have this George Square tragedy when a heavy refuse lorry ran out of control, killing six people and seriously injuring 10 others. By all accounts, it was an horrific incident.
"Just as we were preparing for Christmas, our city of Glasgow is in mourning again."
He offered his "deepest, prayerful, heartfelt sympathies and condolences" to all those who lost loved ones in the incident and added: "We pray for those who were injured in Monday's incident. We are so relieved that they escaped death and we hope that they make a full recovery from their injuries."
Archbishop Tartaglia said the crash "traumatised witnesses and passers-by" and left communities" shocked and saddened".
He told the congregation that Glasgow was now "reeling from this latest sad and sudden tragedy".
He said the "bereaved and devastated families may not feel the joy of Christmas because of their deep sadness and distress" as he spoke of their "grief, their bewilderment, their anger, their desperation, their unanswered questions".
He added: "I wish I could take all that away, but I know that my words are completely inadequate."
A 14-year-old girl left seriously ill after the Glasgow bin lorry crash is one of five patients still being treated in hospital.
The teenager is being cared for at Glasgow Royal Infirmary, where her condition is said to be "serious but stable".
The accident, in which a refuse truck ploughed into pedestrians and Christmas shoppers in the city's George Square, claimed the lives of six people and left a further 10 injured.
Greater Glasgow and Clyde NHS Board confirmed today that five patients are still being treated in hospital for injuries they suffered in Monday's crash.
Two women, aged 18 and 64, are both in a stable condition at Glasgow Royal Infirmary.
Another woman, aged 49, is in a stable condition at the city's Southern General Hospital, while a 57-year-old man being treated at the Western Infirmary is also stable.
A health board statement said: "Five patients remain in three hospitals in Glasgow following Monday's tragic incident in George Square.
"Three patients remain in Glasgow Royal Infirmary. One is a 14-year-old girl who is serious but stable, one is an 18-year-old female and one is a 64-year-old female, both of whom are stable.
"A 57-year-old man is being treated at the Western Infirmary and is in a stable condition. A 49-year-old female, who is being treated at the Southern General Hospital, is stable."
As their names were released the Queen sent a message of condolence to the city in which she said: "Prince Philip and I were saddened by the news of the tragic accident in Glasgow yesterday.
"Our thoughts and prayers go to the families of those who have lost loved ones and to those who have been injured.
"This sad event is made even more difficult as it comes at Christmas time. I send my condolences to all the people of Glasgow."
It is thought the driver may have fallen ill at the wheel as he travelled up Queen Street, causing the bin lorry to strike a pedestrian outside the Gallery of Modern Art.
The truck continued, hitting several other people and coming to a halt only when it crashed in to the side of Millennium Hotel in George Square.
Chief Superintendent Andy Bates said: "This is a tragic incident which occurred in the heart of Glasgow city centre at a time when people were preparing for the festive season.
"My thoughts are with the family and friends of those involved."
Mr Sweeney was a former president of Bramalea Celtic supporters club in Canada, with the club putting a statement on its Facebook page expressing "great shock and sadness" over the deaths.
Relative John Sweeney described himself as "feeling heartbroken'' on Facebook.
He wrote: ''No words can describe the pain. RIP Jack, Lorraine and Erin. Thoughts and prayers go out to the other families that lost loved ones as well.''
Miss McQuade was a student at Glasgow University and also worked at the luxury Cameron House Hotel on the banks of Loch Lomond, where she was described as "one of our brightest and dedicated members of housekeeping staff".
Ms Tait was a primary school teacher at St Philomena's Primary in Glasgow, where head teacher Catherine Gallagher said the "entire school community is deeply saddened by this tragic news".
She added: "Stephenie was an excellent young teacher, dedicated to the children. Our thoughts and prayers are with her family and friends at this time."
Ms Tait had studied at Glasgow University, whose Principal and Vice Chancellor Professor Anton Muscatelli said it was "deeply saddened" to learn of the death of one of its current students and a graduate.
He added: "Our thoughts and prayers are with the families of Stephenie Tait, who graduated in 2006, and Erin McQuade, a first-year student of English literature.
"This is an awful time for those concerned and for the wider university family."
At a prayer service held yesterday morning at the nearby St George's Tron Parish Church the Rev Stuart Smith, moderator of Glasgow Presbytery of the Church of Scotland, said the circumstances of the crash were ''more sudden and shocking than we could have imagined possible if it wasn't for the evidence right here in front of us''.
He said: "In just a few minutes yesterday afternoon, a scene of celebration and festive lights in George Square turned to devastation and despair."
The tragedy struck just over 12 months after the Clutha Bar helicopter crash in Glasgow, which claimed the lives of 10 people when a police helicopter crashed on to the roof of a crowded pub last November.
Ms Sturgeon said while 2014 had been an incredible year for the city, which hosted the Commonwealth Games in the summer, it had been "bookended by two unimaginable tragedies".