People pay tribute to victims of knife attack outside Notre-Dame basilica in Nice, France, Oct. 30, 2020. France''s vigilance against terrorism is raised to the highest level of "attack emergency" throughout the national territory following the knife attack in Nice, Prime Minister Jean Castex announced on Thursday. Early Thursday morning, a knife attacker stabbed to death three people at Notre-Dame basilica in central Nice. The alleged perpetrator has shot by police and transferred to hospital. (Photo by Serge Haouzi/Xinhua)

Candles and flowers are placed outside Notre-Dame basilica to commemorate the victims of knife attack in Nice, France, Oct. 30, 2020. France''s vigilance against terrorism is raised to the highest level of "attack emergency" throughout the national territory following the knife attack in Nice, Prime Minister Jean Castex announced on Thursday. Early Thursday morning, a knife attacker stabbed to death three people at Notre-Dame basilica in central Nice. The alleged perpetrator has shot by police and transferred to hospital. (Photo by Serge Haouzi/Xinhua)

People pay tribute to victims of knife attack outside Notre-Dame basilica in Nice, France, Oct. 30, 2020. France''s vigilance against terrorism is raised to the highest level of "attack emergency" throughout the national territory following the knife attack in Nice, Prime Minister Jean Castex announced on Thursday. Early Thursday morning, a knife attacker stabbed to death three people at Notre-Dame basilica in central Nice. The alleged perpetrator has shot by police and transferred to hospital. (Photo by Serge Haouzi/Xinhua)

A woman pays tribute to victims of knife attack outside Notre-Dame basilica in Nice, France, Oct. 30, 2020. France''s vigilance against terrorism is raised to the highest level of "attack emergency" throughout the national territory following the knife attack in Nice, Prime Minister Jean Castex announced on Thursday. Early Thursday morning, a knife attacker stabbed to death three people at Notre-Dame basilica in central Nice. The alleged perpetrator has shot by police and transferred to hospital. (Photo by Serge Haouzi/Xinhua)

People pay tribute to victims of knife attack outside Notre-Dame basilica in Nice, France, Oct. 30, 2020. France''s vigilance against terrorism is raised to the highest level of "attack emergency" throughout the national territory following the knife attack in Nice, Prime Minister Jean Castex announced on Thursday. Early Thursday morning, a knife attacker stabbed to death three people at Notre-Dame basilica in central Nice. The alleged perpetrator has shot by police and transferred to hospital. (Photo by Serge Haouzi/Xinhua)