First of all, I am sorry for your loss.
Next: Did you file a police report? If not, Why? Crimes like this are not always on the news unless there is an outbreak of the same type of crime. Why don't you watch the news to keep up with the current events in your town. If you can't watch, at least listen to it on the radio or read the paper.
Do you know for a fact it was the person you described? If you had your head turned away, how could you pinpoint a certain person unless you saw it happen? You seem to have great detail on the person who did this. I just don't see how you have that detail if it happened behind your back. Naming a make and model of a car is sharp, as well as describing someone.
Police will ask these questions and more tough ones. Too many times, people are wrongfully accused, not always intentional but accidently as well. What if you happened to see this black guy in the white G6 as he was driving away and you noticed your loss. You assume it was him. It does not necessarily mean it was him, he could simply be someone exiting the station from fueling his own car.
On the times I put gas in my car, I am standing at my car pumping gas, not watching the gas meter.
It is important to always remain cautious and watch your back. I hope you get the issue resolved.