In what is becoming the “new normal” in Europe, there was yet another terrorist attack in France yesterday. It’s hard to keep track of them anymore:

Two women were killed in southern France on Sunday by an assailant armed with a knife, in an attack that forced the evacuation of a major train station, the authorities said.

The assailant was fatally shot by a military patrol after killing the women in front of the Saint-Charles train station in the Mediterranean port city of Marseille. The attack interrupted train service and unnerved the country as it debated the government’s new security bill.

The Paris prosecutor’s office, which handles terrorism cases nationwide, said on Sunday that it had opened a terrorism investigation, but the authorities said the assailant’s motives were not entirely clear.

“This act could be of a terrorist nature, but at this hour we cannot affirm it,” said Gérard Collomb, the French Interior minister, who is in charge of domestic security.

Asked about reports that the attacker yelled “Allahu akbar,” or “God is greatest” in Arabic, at the moment of the attack, Mr. Collomb said that “a certain number” of witnesses had said they heard him do so, but he added that they were still being interviewed by the police for further details.

We may never know the motives behind the mysterious terrorist attacks.