It's not realistic to say that race is never a factor in police shootings. Here? Who knows? Depends on what they thought - maybe knowing they were going to a neighborhood with many African-American residents predisposed them to "fear". Maybe the split-second he saw her was not enough to stay his hand, whereas seeing a woman who looked more like him may have stopped him.
We tend to oversimplify things, especially when we are outraged. Saying race may have been a factor is not in any way saying that these officers went to the house to kill (or execute) an African-American person. Just like she was definitely not killed for having her doors open or her lights on, as some have claimed in their anger. Reality is always more nuanced than that.
In fact, I think the police really did go there to help. I think they saw reason to worry about a home invasion. But flaws in screening, training, and procedures along with probable bias took us to the loss of Ms. Jefferson and the end of a child's innocence. If we can address those flaws and biases on a large scale, maybe we can prevent the next needless killing.