There are always circumstances that are not emphasized. Did he try to flee? Was there and verbal enlargement with the police? Did he get physical? The story says there was reportedly a verbal exchange prior to the shooting.
Why do many young people, especially young black people think they don't have to obey commands given by a law-enforcement officer? Getting mouthy with the police is pretty stupid, as that tends to make them a little nervous.
I carry a weapon every day and have been pulled over a few times while carrying. I always have my driver's license and concealed carry card in my hand when the officer walks up to the window, with the other hand in plain view.
If people would use a little common sense, they wouldn't be getting shot by the police. If the guy was shot in the back, that means he was either walking or running away, and the police already knew he had a weapon.