Heidi Edwards, who is working with the Kenya Human Rights Commission, was inside the upmarket Westgate mall in Nairobi when the attack by Somali militants began.
The lawyer said there was confusion when the blasts first rang out.
“It sounded like scaffolding falling at first, I wasn’t that concerned,” Ms Edwards said.
“Then there was some panic going on and then another one (noise) in quick succession and then some gunshots.”
She found an unlocked “staff only” door leading to a service exit and used the stairs to get down to the ground floor along with a group of people.
“Somebody else, not us, poked their head out and saw a gunman,” Ms Edwards said.
“I don’t know if it was one of the assailants, it might have been a police officer.
“So we had no real choice but to stay in the stairwell.”
When she heard the grenades start up again, “it was clear it was not under control”.
“When they started again it was clear to me that there was someone with a lot of artillery and that was when I started to get quite nervous,” she said.
“There was no sirens which, for a Westerner was quite surprising – if that happened in Australia there would be sirens everywhere.
“It was just confusion more than anything else.”
Melbourne woman Sarah Williamson also survived the attack, with her father who works for the UN.
“She heard the first grenade go off and said, `What was that, dad?’,” mum Linda told Fairfax radio.
“Then he heard the guns firing and he knew exactly what it was and he said, `We’re under attack, everybody to the back of the room.'”
The 23-year-old spent six hours trapped in the store before she could run to safety.
Australian-UK citizen Ross Langdon (pictured) and his heavily pregnant Dutch partner, Elif Yavuz, are among those confirmed dead.
People with concerns about family or friends in Kenya should try to contact them directly or if unsuccessful phone the DFAT consular emergency centre on (02) 6261 3305.