The gunman who killed seven people in three shootings in the south of France could strike again, the prosecutor leading the investigation has said. All the victims were shot in the head at point-blank range, Francois Molins told a news conference in Paris. But he downplayed the significance of a camera which the gunman may have been carrying when he killed four people at a Jewish school in Toulouse on Monday. Three soldiers of North African descent were also shot dead on 11 and 15 March. Schools across France observed a minute's silence on Tuesday morning. The bodies of the four victims are being flown to Israel for burial on Wednesday. Funerals for the murdered soldiers will also take place on Wednesday in France. Mr Molins said the gunman knew he was being tracked and was "likely to act again". Scarlet alert Ballistics tests showed all the victims had been shot with the same weapon, a Colt .45 gun. The killer also used the same model of scooter, a high-powered Yamaha TMAX 130, in all three attacks. However, Mr Molins said it had not been established whether he used the same scooter, as the model seen at the site of the first attack was black, while the one used in the school shooting was white. He also rejected earlier suggestions that the number plate of the scooter had been identified, and said it may not have been a scooter reported stolen from Toulouse on 6 March, as earlier reported. As prosecutor for Paris, Mr Molins has authority over counter-terrorism investigations. For the first time in its history, France is on "scarlet alert" for terrorist attacks, the highest level. The measure enables the authorities to disrupt daily life and implement sweeping security measures. These include mixed police-military patrols and powers to suspend public transport and close schools. About 250 investigators are pursuing two main lines of inquiry - an extremist Islamist motive or the far right. Mr Molins stressed that no line of inquiry was being ruled out. Interior Minister Claude Gueant earlier said the gunman may have filmed the attack in Toulouse on a camera worn on a harness on his chest. The camera "records wide-angle footage that can then be watched on a computer. I feel that that will reinforce the killer's psychological profile," the minister said. He added he did not know if the man had filmed everything. He went on to describe the killer as "someone who is very cold, very determined, very in control of himself, very cruel". Three soldiers expelled from the army in 2008 for neo-Nazi activities have now been cleared of any involvement in the shootings. The three were members of the same parachute regiment in Montauban as the soldiers killed in the attacks on 11 and 15 March. The shootings took place as parents were taking their children to Ozar Hatorah school on Monday. A teacher and three children were shot dead, and a teenage boy was seriously injured. All candidates in the French presidential election have suspended campaigning.