To
Breonna's boyfriend fearing for his safety fired several shots at the plain-clothed men who had just broken into his home. These police officers returned fired, striking Breonna at least eight times.
When most people read "Kenneth got into a brief confrontation with John. John then fired four rounds at Kenneth." they will assume brief confrontation means "shouting and cursing match" or "physical altercation" not "fired a gun at".
Your home, your legally owned gun, your panic and chaos, you shoot. I would do the same, I would not be surprised that others did the same.
Expectation of professionalism, and de-escalation is on the regulated authority with power and accountability. If they were well trained, and made a calculated risk for an important case, they may be justified. From all that I can find, it seems clear to me that the police acted unprofessionally, and anything past that is not really a factor until that unprofessional behavior is addressed.