Could be, but that wouldn’t be my first inclination since the rest or the bullets hit him in his front. The only reliable witness at this point is the cop and I haven’t read his full account.
I’m thinking of two possibilities:
1. He was falling forward from the effects of previous shots to his arm and torso.
2. As he closed the distance to the cop, he lowered his head to bullrush him.
Purely speculation on my part, of course.