Do you know that even an over weight person can cover 7 feet and stab you in less than 1 second.  Do you think you have time to make decisions of life and death if it comes down to you or the perp with mental issues?  Easy huh?  Can you  raise a gun and take aim in less than one second much less make the decision to pull the trigger?  Condolences to the family of the woman and also the officers involved.  No officer wants to shoot anyone knowing the repercussions, believe it.