Hundreds of redundancies at Aberdeen's last paper mill came "totally out the blue", devastated workers have said.
Stoneywood paper mill - which has operated for more than 250 years - went into administration on Thursday with the loss of more than 300 jobs.
Calum Mackay, who worked at the mill for 10 years, told BBC Scotland it was a "hammer blow".
Scottish Enterprise has given the mill owners more than £12m worth of support over the last three years.
In 2019, the business was sold to a new parent company, securing the jobs at the mill.
However, administrators have now been appointed at the Arjowiggins Group mills at Stoneywood, as well as Chartham, Kent, with 368 of the group's 463 UK-based employees made redundant immediately.
A total of 301 out of the 372 members of staff in Aberdeen have been made redundant.
A total of 95 staff have been retained to continue limited activity at the two sites while the administrators explore the possibity that the sites and assets could be sold.
Mr Mackay, who was the union convener at the mill, said workers were told on Thursday afternoon to attend a meeting an hour later.
He said: "We were told that we were redundant, they had exhausted every avenue they had to try and keep the place open.
"We had been expecting a buy over, unfortunately instead we got a hammer blow.
"Obviously it was no surprise to any of us to the learn the company was in trouble, that had been the case for a long time, since 2019 we've had severe issues, and the management team have struggled to keep the operation going."
He described the sudden news of administration as "an absolute shock, totally out the blue".
Mr Mackay said: "The site has been here for 252 years, an awful lot of the families that were here 252 years ago are still here.
"It's devastating, very distressing."
He said many staff members were in the later stages of their working life.
"They are going to struggle, they really are," he said.
"It really is the end of an era, a large part of Aberdeen's history revolved around mills, to see it go, it's a tragedy for the area, it's a tragedy for Scotland.
"It marks the passing of a once-great industry."
Shauna Wright, of the Unite union, said workers were saddened at the sudden news.
"None of the members were expecting anything like this at all," she said.
"It really hasn't sunk in to a lot of our members, we are still trying to understand how did this happen so quickly."
A mass meeting is being organised for next week.
The Scottish government described the situation as "concerning".
"This will be a very uncertain time for the company's staff, their families and the local areas, which will be affected by this decision," it said.
"Scottish Enterprise will work with the administrators to understand the potential options for the business going forward and explore all possibilities to rescue the jobs."
Scottish Enterprise said its interventions had helped maintain an important employer's presence in Aberdeen and protect employees' jobs since it first went into voluntary administration in January 2019.
"Our decisions to support Arjowiggins were based on a shared view, alongside private investors, that the company had a viable future," it said.
"However, conditions deteriorated and despite the best efforts of everyone involved it was not possible to secure a sale of the business as a going concern."
The mill had been bought for an undisclosed sum in September 2019 by subsidiaries of a new venture, Creative Paper Holdings Ltd.