He probably meant grabbed him by the arm or neck through the window. Dorian Johnson stated he grabbed his neck through the window. He obviously didnt mean "pulled his whole body through the window".
With likelihood in mind, how likely is it that a person believes they can grab a holstered gun from a cop, get shot, decide to run at least 150 feet from fear of getting shot again, and then turn into a 'demon' with no fear of gunfire anymore and charge the source of gunfire?
With that and some other odd aspects of his behavior which Johnson claimed was out of character (eg starting an alterction and stealing in the store), I wonder if he was suffering from Toxoplasmosis or some similar condition. Toxoplasmosis is thought to dramatically affect an individual's appetite for risky behavior. Preliminary research suggests that as you'd expect there 's a higher seroprevalance in prison populations, but much more work needs to be done to verify this.