At no point did the kid enter the car. You want us to believe that a teenager, starting college the next day, dove into the drivers side of the car to steal a police officers gun. Picture that for a second and if that doesn't make you laugh then i don't know what will. The eyewitness accounts make the most sense so far.
Secondly, the gunshot to the back doesn't make sense. The gunshots while his hand were up also doesn't make sense. It seems like the cop was wrong on a number of levels.