The Police have already said there is a lot of infortmation that hasn't been released to the public. What we do know is that the weapon and holster were located on his waistband. That was reported by Officer Smith who was there on the scene.
Aiming isn't too much of a problem with someone at point blank range, and one doesn't cooly need to reach for something when after a few seconds of being knocked around, you realize that some relief is at your fingertips. The desire to stop the puches by covering your face isn't as great as the desire to end it by reaching for your weapon.
None of us know enough about the details to form an opinion as to how it might have played out in real time.
The word “coolly” was tongue in cheek. Still, when somebody is pounding you with his fist, you have to free one hand to reach for the gun, opening yourself to more hits.