Actually it shows much more then that. It shows Brown accosted the officer in the car and in all probability the blood on the gun was from either blood spatter from being shot or blood from Brown trying to take the gun. Given there was no injury to Brown evidenced in the video inside the store he had to have gotten it with his struggle with Wilson inside the car. The evidence corroborates Wilson's story not bystanders.
a hahahahaha
funny