A man with a knife killed two women at the main train station in the French city of Marseille on Sunday, shouting “Allahu akbar” during an attack that French authorities were working to determine had links to Islamic extremism.

Interior Minister Gerard Collomb, who went to Marseille to meet with local authorities and troops on the scene, said local police have video that shows a man attacking a woman and running away, then coming back and attacking a second woman.

The video shows the same man running toward soldiers who were rushing to Marseille Saint Charles train station. The soldiers fatally shot him and both of the women died of their injuries, Collomb said.

Some witnesses reported hearing the assailant shout “Allahu akbar,” Arabic for “God is great,” Collomb said. He said the attack might have been of a “terrorist” nature, but that authorities could not be sure until the investigation progressed.

The Paris prosecutor’s office, which oversees all terror cases in France, said it had opened a counterterrorism investigation of the Marseille attack. It did not provide further details, including a possible motive.

Police sources told The Associated Press that one of the victims was stabbed and one had her throat slit. The officials spoke on condition of anonymity because they weren’t authorized to speak publicly about the investigation.

Collomb declined to provide any details about the suspect or to identify the victims. He said the assailant’s “strange” behavior of attacking, running away and then returning to strike again was “a point of inquiry.”

Earlier this month, four American college students were attacked with acid at the same Marseille train station. French authorities said the female assailant who doused the four Boston College students was suffering from a mental illness and her actions were not investigated as a terror attack.

French President Emmanuel Macron said he was “deeply outraged” by Sunday’s “barbarous” knife attack. In a tweet, Macron paid tribute to the French soldiers who responded “with cool head and efficiency.”

The French government this month decided to maintain the so-called Sentinelled Operation military force of 7,000 soldiers that was created to protect sensitive sites after the deadly extremist attacks of 2015.

Saint Charles train station was evacuated and closed for several hours after the attack, and Marseille police warned people to avoid the area, tweeting that an operation was underway. Soldiers and police took up positions outside the station.

The train station was partially reopened in the late afternoon and French authorities allowed train traffic and from Marseille to gradually resume.

Story by the Associated Press