I have several conflicting thoughts about the violence.
First and foremost, violence of this type forecloses non-violent options. I don't think those were exhausted before by any means. But now look: #BlackLivesMatter discredited, to many minds. Police violence justified to many minds. Has or has not this event damaged the chances of political resolution? Given the circumstances and the political damage, I'm going out on a limb and saying sniping these police officers was unconscionable. (More on unconscionable later.)
Second is an open comment directed to those who refuse to recognize the circumstances under which blacks live, which are oppressive. Enthusiastic supporters of the Second Amendment endlessly remind us that its purpose is to ensure the people can "overthrow oppression." This
is what overthrow of oppression looks like: it looks like murder...to the oppressors. This is how the "Minutemen" we're so proud of looked to the British. Think about that.
Next, a comment on tragedy. The death of Alton Sterling was a tragedy. The death of Philando Castile was a tragedy. The deaths of five officers today was...five tragedies. These aren't separable by degree. It isn't any more acceptable to shoot "that thug" than it was to shoot these officers; and a big part of the problem is those who think there is a difference. Not anyone in particular, but quite a few people in general...starting with those who immediately set out to prove every dead black man was "a thug" and, therefore, his death was "a service" not a tragedy.
Bombing of the suspect. Yeah, the Philadelphia police did that once upon a time, and it was a PR disaster. From the Wikipedia article on MOVE, 1985 Bombing
The MOVE Commission issued its report on March 6, 1986. The report denounced the actions of the city government, stating that "Dropping a bomb on an occupied row house was unconscionable."
Well we'll see, won't we? But I kind of think this bombing was unconscionable, too. Bombs tend to be indiscriminate killers.