On 15 June, Glasgow School of Art's Mackintosh building was finally completely destroyed by fire. I remember well my first day of work there in March 2000. I was awestruck by my new surroundings. My favourite space was the library, as it was for so many people. I cried in 2014 at its destruction.

As with the first, in retrospect relatively minor, fire there has been an outpouring of grief. It is a tragedy for Glasgow, Scotland, GSA and everyone past and present associated with it. But this time, there is also anger. I've been thinking about what the late, great architectural historian Gavin Stamp would have been saying today. He would have been saying that it was an obscene and avoidable act of destruction. And he would have been right.

People are cautioning, correctly, against attributing blame prior to the investigation. But much of the anger is about GSA's refusal to take any responsibility – for either fire. Of course an investigation must take place to determine the cause of this latest disaster; but the immediate cause isn't the crucial point. The real question is, why? And why twice?

Two press statements have been released by GSA. Both seem to abrogate
responsibility, saying that 'The Mackintosh building was undergoing a period of restoration following the fire in 2014, with management of the site under the control of main contractor Kier Construction Scotland and was not part of our operational estate.' Kier responded in a statement last night claiming it had an 'agreed' fire safety strategy.

The chair of GSA, Muriel Gray, rather more subdued than in 2014, tweeted that she had received 'beautiful' responses. But there is nothing beautiful about this tragedy. The destruction of one of the world's most precious architectural gems is an act of violent, ugly, careless destruction. And for that – regardless of whatever the new investigation finds – GSA bears at least some responsibility.

In truth, the seeds of the Mack's destruction were sown long before both fires. Members of staff and alumni who raised issues about the safety of the building for years prior to 2014 had to remain tight-lipped after the first fire, or condemned as churlish in the wave of sympathy and grief.

Fire experts are shaking their heads in disbelief. Where, they ask, was the full modern preventative technology that exists for life safety and property protection? Why, as reported, was there only one security guard on site – located in a Portakabin outside the building?

Tom Inns, the director of GSA, announced in 2014 that lessons would be learned and that the school had been working hard on its health and safety procedures. As to the fire report, Inns went on to say: '[It] is very detailed about how the fire spread; that gives us a lot of new knowledge that we need to take on board.'

But the 'knowledge about how the fire spread' had been known for decades. Gordon Ross, a senior technician at GSA for 17 years, routinely carried out fire assessments with the then clerk of works, David Stark. Ross repeatedly warned that GSA was at serious risk of fire from the old heating system which used wooden ducting to take warm air from a boiler room in the basement to the rest of the building. That system should have been closed to prevent it funnelling fire from the basement to the roof in less than five minutes. Ross and Stark recommended strongly that these 'wooden chimneys' be blocked off and a sprinkler system fitted. Their recommendations were not implemented.

To be fair, management is not entirely to blame, even if it's tempting to do so in anger. Few institutions are located in, or responsible for, a world heritage site. However, why weren't these recommendations implemented during the £8m refurbishment of the building in 2008?

You might argue that the Mackintosh building is not 'the GSA,' but it is. A reputation as one of the finest art schools in the world is directly attributable to that building and the outstanding creative community that has emerged from it. Its magnificent interior, against which the annual degree show was curated, was the real star of the show.

And therein lies part of the problem. The degree show was an annual nightmare for the estates department, the Mackintosh curator, the health and safety officer and many others. Year after year, concerns were vocalised about the damage inflicted on the building – actual and potential. But apart from a few minor adjustments and eye-rolling, little was done, and the interests of the building were often sacrificed for artistic freedom. The fine line between use and abuse was raised repeatedly, and in many cases crossed, none more so than prior to the 2014 fire. Why did the management of GSA, despite warnings, allow a student to combine expanding foam with a hot projector in the basement of so precious a building?

A former health and safety officer has reported to me that following the fire he became aware that the student whose project caused the incident had been told by members of staff, including a head of department and an estates electrician, to stop working with flammable aerosols. The consequences could have been much worse: students and staff vacating the building were minutes from inhaling deadly fumes. This was avoided by the prompt and brave action of a member of the academic staff.

When I worked there, prior to the 2014 fire, I (and other colleagues) noticed a perceptible whiff of disdain for Mackintosh in GSA's strategic push to be all things contemporary. Only since the 2014 fire has there been an upsurge in the school's promotion of research focused on his genius and masterpiece.

In the early noughties the powerful communications team expunged GSA's
headed writing paper, with its depiction of the Mackintosh façade, replacing it with something bland, generic and completely forgettable. Their response to the fire in 2014 was magnificent in its own way. While experts grew frustrated that the causes of the 2014 fire were not being handled transparently, GSA pushed a narrative of phoenix from the ashes. Medals were given to fire-fighters, and Brad Pitt was enlisted to the cause. Much-needed funding was generated. But the official narrative was far from the whole story. Very serious questions remain.

I was recently told a small but significant detail. In September 2014, GSA held a symposium about the rebuilding of the library. Chaired by the BBC's Stuart Cosgrove, it was intended to inform the construction and restoration plans. Where was the symposium held? House for an Art Lover? Glasgow Atheneum? No, it took place in Venice, apparently to coincide with the Biennale. The costs of this extravagance raised eyebrows at the time, but such was the hype that few spoke up. One Glaswegian attendee was scathing, and told me: 'It was an obscene junket.'

The punishment for hubris is its inevitable downfall. The Mackintosh building was built for painting and sculpture. Its wooden interior – soaked in linseed oil and turps for 100 years – had survived cigarettes, the second world war, and even toasters. What it was unable to withstand was not only fire, but hubris, flammable aerosol cans, and, with tragic irony, restoration.