While the usual groups are taking sides, largely based on race, take race out of the equation and look at the timeline of events.
A neighbor called the police for a welfare check because he saw his neighbors door open at 2:30 am.
They haven't released the 911 call so we don't know exactly what the cops were told. Did the 911 operator change 'welfare check' to 'suspicious activity', 'possible burglary in progress'?
The cops arrived. Instead of going to the open door, knocking, or ringing the doorbell, they instead walked around the house.
Apparently the woman was playing video games with her nephew, she heard a noise, and took out her gun. Based on the Castle Doctrine she had ever right to reach for her gun to protect herself, her nephew, and her property. Since the police didn't identify themselves, she had no way of knowing they were 'the good guys'.
The cop looks in the window, doesn't identify himself, shouts at her, and then shoots.
If it's 2:30am and you hear a noise outside, is your first thought, 'it must be the police'?
The woman acted in her own defense as anyone would.
I'm not calling the cop a murderer. However, protocol wasn't followed. The cops didn't knock or ring the door bell. The 911 call only asked for a welfare check. The cops never identified themselves and they shot within seconds of seeing a person; not even a 'suspect' (there was no reported suspect). There was no reported crime. This was simply a 'welfare check'.
The key may be in the 911 call and how the call was relayed to the cops investigating.
Dispatch audio has been released. Also, the two officers rolled up and spoke to the caller before performing the welfare check.