"We are up against an extremely determined individual, who knows he's being hunted, who could strike again," Paris Prosecutor Francois Molins told a news conference, saying the victims had been shot at point-blank range.
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"No leads have been ruled out at this point...None will be neglected or abandoned until the author of these crimes is arrested," he said.
On Monday French media outlets reported that the same 45-caliber weapon and the same stolen scooter used by the gunman during the attack on the Jewish school had been used in the two previous shooting attacks in Toulouse and Montauban.
French police have stepped up the manhunt for the killer, who, according to Interior Minister Claude Gueant, had a camera around his neck while attacking the Jewish school and may have filmed the scene.
The minister described the killer as "someone who is very cold, very determined, very in control of himself, very cruel".
One police officer involved in the investigation told Reuters, "It would be surprising if he stops now."
The attack on the school prompted President Nicolas Sarkozy to put the region on its highest terrorism alert, and more than 100 police officers were dispatched to the area to hunt for the gunman.
Three French soldiers killed last week (Photo: AFP, SIRPA)
Security was tightened in Toulouse, guards were posted at religious sites and the terror alert level was raised to scarlet, meaning 'imminent attack', for the Midi-Pyrenees region.
Sarkozy said the killings at the school and those of the soldiers, one of Caribbean and two of Muslim origin, appeared to be motivated by racism.
"In attacking Jewish teachers and children, there seems to be an obvious anti-Semitic motivation," he said late on Monday. "With the soldiers ... one can imagine that the bloodthirsty madness was linked to racism."
Police had not named a suspect but said they were searching the city of around one million for a man they believed could be a trained marksman, as well as the Yamaha motorbike he used to flee. The shooter's face was hidden by a motorcycle helmet during the attack.
A female witness told French television the gunman appeared to have a tattoo on his face when he lifted his visor.
One weapon, a powerful automatic handgun, had been used both in the school attack and last week's shootings of the soldiers.
Also Tuesday, France Info reported that three former French soldiers who were suspected of involvement in the deadly shooting at the Jewish school in Toulouse have been cleared of all suspicion.
Meanwhile, Ynet has learned that the Ozar HaTorah School will reopen Wednesday. "The children are in shock, but they need to be here (school)," a member of the local Jewish community told French media.
French Foreign Minister Alain Juppe is expected to arrive in Israel Wednesday to take part in the funerals of the Jews killed in Monday's attack.
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