There is a very prominent young black economics professor at Harvard—I think maybe the youngest black to receive tenure there—who did a study with similar results. Essentially cops are more fearful of the impact of shooting blacks and so more hesitant to do so, even in threatening situations.
However, apparently there is more gruff treatment of black suspects than white suspects. It is just that they are more likely to shoot and kill the white suspects.
This is Mother Jones, I know, but the article discusses the study you mention and seems relatively impartial: http://www.motherjones.com/kevin-drum/2016/07/new-study-suggests-police-shoot-whites-more-frequently-blacks