There is only one person responsible for the deaths of these officers.
There are muliple people responsible for enabling the perp, but ultimately the perp is the only person responsible for this killing. He made the choice to take those lives that day.
Don’t get me wrong. I agree every person responsible for enabling the perp all along the way should pay with their careers, or their freedom, and each should sued by the survivors of these officers. There should be no protections for any of these folks, either the ones outside the law, nor those responsible for upholding the law.