I searched for statistics on police shootings of unarmed people, and I couldn't find much. It turns out no one really collects statistics on this. I guess local police offices do but they don't get collated by any federal agency. I would think that at least local newspapers report on each one and someone like Google or using Google could collect the info, but if someone is doing that I didn't find it.
The most informative I found was this. In August Jaeah Lee wrote in Mother Jones Exactly How Often Do Police Shoot Unarmed Black Men?. They updated it with a link to a USA Today article, Local police involved in 400 killings per year which collecting some statistics says on average, twice a week a white police officer kills a black person. It's not at all clear about the circumstances of these.