A knife-wielding attacker stabbed three people, killing one, before being shot by police in Australia’s second-largest city Melbourne on Friday, police said, adding that they didn’t rule out terrorism as a possible motive.

The man was taken to the hospital under guard and is in critical condition, according to police in Melbourne, who said they had been confronted by the attacker when they responded to reports of a vehicle on fire in the downtown area.

Police said there was no known link to terrorism “at this stage” but that investigators were “keeping an open mind.”

Vehicles have been used in prominent terrorist attacks in recent years, including in Barcelona, London, New York and Nice, France.

Images captured in Melbourne on Friday showed a burning vehicle and smoke rising above the high-rise district.

Footage published by the Australian Broadcasting Corp. showed a man lunging and slashing at officers with what appeared to be a knife, while a car was on fire a few yards away.

In December last year, an Australian man of Afghan origin plowed a car into a crowd of people, injuring more than a dozen; one victim later died.

That took place just blocks away from where Friday’s events were unfolding.

Police at the time said it wasn’t likely the December incident was terrorism-related. During a legal hearing in September for the man, Saeed Noori, the prosecutor said that Mr. Noori had uttered “Allahu akbar” several times after he was arrested, according to a report from the ABC.

The phrase means “God is great” in Arabic. Mr. Noori pleaded not guilty to a murder charge and 15 counts of attempted murder, local media reported. In January 2017, another man drove a car through Melbourne’s downtown and killed six people.

The ABC reported that man was considered to be in a drug-induced psychosis and the attack wasn’t considered terrorism-related.

He is on trial this week.