Here, the man was armed with a gun (albeit unloaded). He was unstable enough for his girlfriend to put the police on suicide watch during her 911 call. If the police had to take classes on handling various situations, this particular scenario would be a final exam question. Moreover, I'm afraid that a majority of our policemen would have flunked this question.
Law enforcement is meant to be complex, and should require sophisticated knowledge in law and philosophy as prerequisites for aspiring policemen. Each police officer working on duty is not only serving as the enforcer but also as a judge. He judges whether a subject should be let go, detained, or - shocking as it may seem - be put to death.
A well functioning civil society founded on the idea of some social contract is bound to provide its citizens with some rights and protection. The prospect of summary execution at the any sign of threat to its law enforcers appears to fall short of this requirement in my eyes.
The officer in question in the topic being discussed, Stephen Mader, acted ahead of his time. He demonstrated the form of policing possible in our society with further sophistication of the minds of our officers. He took decisions that prioritized the right (to life) of his citizens. He was fired for doing so.
I am sure he would have shot Mr. Williams, having had his gun trained on him, had he chosen to make any threatening move.
It is a fine line, I admit. But is this not what progress is based on? Have we not advanced our civilization by continuing to investigate finer and finer still of dimensions? Why do we continue to rely on such crude measures when it comes to law enforcement? Are we incapable of serving our citizenry with increased space for preservation of their rights?