Virtually everyone the police come into contact with is either under the influence of drugs, suffering from some form of mental illness or intent on not being around the police to the point where they'll attack them in order to get away. Best case scenario for the cops is dealing someone who is just having a really bad day. Cops aren't able to diagnose autism within seconds of arriving on scene. Neither are experienced psychiatrists. Either might be able to take a guess and it might well turn out later that they were right, or it might turn out that the person had a history of violence and was high on ice at the time and ready to slash the throat of anyone who looked at them a bit funny. People with autism spectrum disorders can be violent and act irrationally anyway. The woman had been threatening to run out into the heavy traffic, presumably with the intention of being hit by a passing vehicle. The cops had tried using capsicum spray, which was ineffective and a taser, which was apparently also ineffective. The cop who fired was caught between the woman holding a large knife and a busy road and, from the reports, backed away towards the road to avoid shooting for as long as possible.