Workers whose colleague was killed in an earthquake in Christchurch were concerned about cracks in an adjacent building that subsequently fell outwards during the tremor.
An inquiry is being held into earthquakes in Canterbury that began in September 2010 and included the fatal quake on 22 February last year. The region continues to be hit by significant quakes.
The Royal Commission is hearing evidence about three buildings in Cashel Mall where walls of the middle one fell against the others in February.
Four people died when the building at 91 Cashel Street fell against the buildings on either side. They were: bakery worker Shane Tomlin and shoppers Melissa Neale, Christopher Homan and Jillian Murphy.
The Royal Commission heard Mr Tomlin was found on the ground floor of the Trocadero Bakery and taken to hospital, but later died.
Beverly Broomhall worked at the bakery with Mr Tomlin. She told the commission on Tuesday she had been worried about the building next door which she said had long cracks and was on a lean.
After the shaking began on 22 February, she said she saw lots of dust and heard another colleague calling for Mr Tomlin.
Ms Broomhall then heard an almighty crash and looked up to see the sky. She said she considered jumping out the window because she was so scared.
Another colleague, Jan Smith, believed the cracks in the building had grown much worse following a quake on 26 December 2010.
The owner of the middle building that failed told the hearing on Tuesday that no quake strengthening had been done on it because none was required.
Tracy Gough said he had not carried out structural or strengthening work because he planned to redevelop the site.
He said after the September 2010 quake the building was red-stickered until loose chimney bricks were removed.
Mr Gough says he relied on council advice and assumed that when the placard was removed, the building would be safe.
He admitted he did not organise a more detailed inspection that was recommended.