of. >> since the sydney attack by a gunman, australia very much on the edge. >> an attack is likely. we don't know when and how an attack may come with the intent and capability ocarry out further attacks. >> reporter: the sydney gunman, the late nest a series of attacks, often by people with violent criminal backgrounds and mental illness. >> we have to consider that isis is almost a magnet for the diluted and the mentally ill to associate themselves. as soon as they put the banner of isis behind it, it has a major repercussions to the gravitas they think their actions are taken. >> security now being increased across france, after three attacks in the past three days. on saturday, a man stabbed, three police officers while allegedly shouting god is great. on sunday, a vehicle rammed into pedestrians, witnesses said the