Bowers is ultimately accountable for the shooting of course, not anyone else - not you, not me, not anyone here at Websleuths, not anyone outside of WS, not the President, not the gun manufacturers, no one else.
There is something called individual action and personal accountability - Bowers made the choice to shoot this particular synagogue and the worshippers - a truly heinous crime.
But there is something even more dangerous at play here: collectivism. In simpler terms, the failure to recognize individualism, one's individual actions, - it seems like every single time a mass shooting takes place in America, it is always everyone else's fault except the shooter's. Of course, I disagree with that.
It is highly doubtful Bowers will receive the death penalty; at worst he will receive a slap on the wrist.
Unfortunately, slaps on the wrist have not deterred crimes like this, it simply exacerbates them.