Its sad he was shot, but it was almost inevitable after two officers saw he had a gun resting in his lap. Inevitably, when the police woke him up, any semi-conscious movement could have been interpreted as an intent to use the weapon. Looking at it now it would have been better to block and contain the vehicle and then smash the windows out from a distance and use bean bag or pepperball rounds until the driver woke, then deal with him from there. I don’t understand what the hurry was to deal with him in an unsafe way - it was almost inevitably going to lead to shooting one way or both ways - amateur really.
As for the number of rounds fired, its standard, even here in the UK, for police to continue firing until they cannot any longer see the threat. There is no question of warning shots or shooting to wound or firing a single shot or any limited number of shots. Once the police start firing, their intention is to kill.
Again, I have never heard police anywhere having a policy of starting to shoot when first fired at. They shoot at threats, not just shooters. And in this case, McCoy had a visible weapon. It was found later to have been stolen and an extended magazine fitted. There seems little doubt he intended illegal use of a fire-arm.