Tasmanian-born architect Ross Langdon and his Dutch partner Elif Yavuz, who were expecting their first child in just two weeks, were gunned down by Islamist attackers at Westgate shopping centre at the weekend.

“We have lost my beautiful son Ross Langdon, his lovely partner Elif Yavuz and their much loved baby just two weeks away from birth,” his mother Linden Langdon wrote on her son’s Facebook page.

“The loss is immeasurable, absurd and excruciating.”

Former US president Bill Clinton paid tribute to Harvard-educated Ms Yavuz, who worked with the Clinton Foundation during her doctoral studies and recently rejoined the institution as a senior vaccines researcher based in Tanzania.

Mr Clinton, former US secretary of state Hillary Clinton and their daughter Chelsea say they were “shocked and terribly saddened” to learn of Ms Yavuz’s death.

“Elif was brilliant, dedicated, and deeply admired by her colleagues, who will miss her terribly,” they said in a statement.

“Elif devoted her life to helping others, particularly people in developing countries suffering from malaria and HIV/AIDS.

“On behalf of the entire Clinton Foundation, we send our heartfelt condolences and prayers to Elif’s family and her many friends throughout the world.”

Australia’s new foreign minister Julie Bishop extended the government’s sympathies to the families of all victims of the mass shooting.

Ms Bishop, who is in New York for the UN General Assembly, condemned the “brutal attack on innocent civilians”, saying the death of London-based Mr Langdon and others are a reminder that “we must do all we can to fight terrorism”.