A knife-wielding man killed two people and seriously injured another victim near Paris on Thursday, French authorities said.
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The attack occurred in Trappes, a suburb about 20 miles southwest of Paris, officials said.
The suspect entered a villa where his mother lived and killed her and his sister, authorities said.
A third victim, whom the Associated Press identified as a woman, was stabbed outside. That victim, who was gravely injured, was not a relative of the suspect, according to Collomb.
After emerging from the home, the suspect, still armed with the knife, threatened police officers, according to French Interior Minister Gerard Collomb.
Police shot and killed the man after he ignored their commands, authorities said.
Authorities have not identified the man nor disclosed a possible motive.
An online statement from the Islamic State group's news outlet claimed the attacker was an ISIS fighter, but French authorities have not confirmed that report.
"The attacker in the city of Trappes, South-West of Paris is an ISIS fighter and carried out the attack as a response to the calls to attack coalition citizens," the Amaq News Agency stated, citing an unknown security source.
Collomb told reporters that the suspect had "serious psychiatric problems" and was "known" for spreading terrorist ideology. However, Thursday's incident was more of a case of a mentally unstable individual rather than someone who was committed to terrorism and might respond to calls from ISIS, according to the minister.
Authorities are working to establish the "circumstances" of the attack, Collomb added.
French anti-terrorism prosecutors have not yet opened an investigation into the incident.
In the wake of the attack, Collomb visited Trappes, where he was seen shaking hands with police officers and other first responders. He offered his condolences to those impacted by the deadly stabbing and commended local law enforcement officers for their quick response.
"My first thoughts are with the victims and their loved ones. I want to salute the reactivity and the exemplary mobilization of our police forces," the minister said in a statement in French on Twitter.
#Trappes : l’individu a été neutralisé.— Gérard Collomb (@gerardcollomb) August 23, 2018
Mes premières pensées vont aux victimes et leurs proches.
Je veux saluer la réactivité et la mobilisation exemplaire de nos forces de l’ordre.
Elles enquêtent d’ores et déjà pour établir les circonstances de ce drame.
"They are already investigating to establish the circumstances of this tragedy."
ABC News' Paul Pradier contributed to this report.