Five people were killed in a stabbing rampage Saturday afternoon at a crowded major mall in Sydney, Australia, prompting the police to declare a critical incident and evacuate the area.

The attacker was shot and killed by a lone police officer who was directed into the mall by people fleeing the scene, police said. The officer was following the man with the knife. When he turned to face her and raised the weapon, she opened fire, saving lives, Anthony Cook, police assistant commissioner for the New South Wales Police, said at a news briefing.

The attacker acted alone, and there is no continuing threat, he said.

The assailant stabbed about nine people as he moved through the mall Saturday afternoon, Mr. Cook said. Some of the injured are in critical condition, including a small child, according to police.

Yan Zhuang and Isabella Kwai contributed reporting.

This is a developing story.