Nonsense.
They were no longer grappling mano a mano - the perp had disengaged. All was needed at that point was for Slager to contact backup to vector in, swarm the guy take him into custody. I have seen situations worse than this first hand where there were no shootings and the perp was taken alive and straight to jail without a stop at the hospital. This cop is beyond toast - and you'd think after the events of the past year or so officers would be alert to the fact they are under a microscope and adversarial groups are looking for screw ups they could use to their advantage. This clown has handed the militant left a present on a platter, giving their hostile agenda an air of legitimacy.