Ephraim Mirvis, the UK's chief rabbi, has revealed his family were caught up in the terror attack.
He told Mornings With Ridge and Frost he was flying to Sydney tomorrow after the "devastating" attack to be with the Jewish community in its seven-day period of mourning.
"Last night, my wife was checking up on family of ours - I have a cousin and his wife in Sydney. 'How are you?' And they said they were at the event," he said.
"For 15 terrifying minutes they were hiding under a doughnut stand, as people to their right and left were being shot dead.
"This morning they went to synagogue to say prayers of gratitude, but they were among the fortunate ones. So we're feeling this very deeply right now."
Asked if he was fearful that a similar attack could happen in the UK, Mirvis said: "I'm fearful for all of our society. This is not a Jewish problem. It's a problem for all of our society."
Watch the full interview