The point is that the police could have waited. They proactively murdered this man for no reason at that point in the situation. If this individual was white, Hispanic or even Muslim... they would have waited.
They could have waited for him to escape through the ventilation systems and kill more people? They could have waited for him to detonate the entire building and bring it down on everybody’s head, with more police inside and media watching? Either are possibilities they could have waited for and everyone would be second guessing those scenarios just like people are second guessing this one now. I don’t like the idea of robot bombs killing people, but when someone is shooting at police and not negotiating, I do support them taking out the threat and wouldn’t call it murder. Self-defense or defending innocents are probably better terms. And your statement that they would have waited if he was a different race is ridiculous. So you know better what would have happened than the african american chief of the Dallas police? You’re not helping the situation in this country by making these uninformed statements.
There is a point when you present such a threat to public safety that a military solution is required. Hardened criminals who are obviously on a murder spree have given up their right to due process. If he had peacefully surrendered he would have had a trial and his due process (and hopefully hanged for his crimes).