A senior French police officer and his female companion were killed following an attack Monday evening by a knife-wielding man in a distant suburb of Paris, officials said.
The attacker was also killed in the ensuing confrontation with police, while a 3-year-old boy was rescued by officers.
ISIS' Amaq news agency cited an unnamed "source" as saying an ISIS fighter carried out the attack, but the extremist jihadist group hasn't officially claimed responsibility.
The police commander was stabbed to death outside his home in Magnanville, about 35 miles west of Paris, Interior Ministry spokesman Pierre-Henry Brandet told reporters at the scene. The attacker then retreated indoors before elite police commandos stormed the residence. The woman and the attacker were found dead; the boy was found safe.
"The toll is a heavy one," Brandet told reporters, his voice shaking with emotion. "Thankfully, a little boy was saved. He was in the house. He's safe and sound. He was saved by police officers."
Vincent Lesclous, the state prosecutor for Versailles — who said he knew the slain commander — told reporters that the boy was "shocked but unharmed."
"The investigation is beginning. We have no serious [indication] on the motivation behind this act," he said, adding that the assailant's identity was unknown.
If the crime was organized or inspired by ISIS, it would fit in with a long-established pattern of jihadist violence. France, like other countries in Europe, has seen a series of stabbings aimed at police officers or soldiers.