I am sure that it is their training because it happens over and over again.  Police try to do a good job.  They are trained to immediately confront suspects and if the suspect does not submit instantly to use any force, including lethal force, to subdue him.  That's the way it is.  That't the way they are trained.  Police do not take cover generally.  They confront in the open and use deadly force if they feel threatened.  No waiting, no talking, no time for rational thinking.  Just confront and control at any cost.  If you have any evidence that confront and control is not the basic training doctrine, please let me know.