Oh, yes, he does. If you pay attention to the video McDonald states that he "snapped the pistol" in other words he pulled the trigger. Innocent people certainly don't try to shoot their way out, now do they.
Even if he did "snap the pistol" like embellisher McDonald claimed, that doesn't mean he was trying to shoot anybody. Furthermore,
CT Walker said that he saw several hands on the gun before it ever came out, and that when he heard a soft click (which Ray Hawkins said could have been somebody in the seats making a noise) the gun was pointed at a 45 degree angle and slightly toward the screen. Not only that, but McDonald said on day one that the gun misfired. The bit about sticking his hand between the hammer and the firing pin came later. And Paul Bentley claimed that
he was the one who prevented the gun from firing.
So, there's no good reason to think that the trigger was necessarily ever pulled, and if it was there's no good reason to think that it must have been Oswald who did it, or that it was aimed toward a cop at the time.