Except the first shot did not occur until after the agent was struck. Considering the split second decision that had to be made about the uncontrollable nature of the situation, it seems a reasonable action by the agent (he did not know how bad he was hit, where he would end up if knocked down or what direction change of the vehicle might occur, etc.). The problem with all the analysis (YouTube or in print) is it is all discussing things after the event with the help of slow motion video, multiple angles, etc. and the law requires the judgement to be made without that.
Again, we shall see how the criminal issues proceed with the investigation, and who knows how political bias will play into that process (hopefully not a lot). As to the civil case(s), just keep in mind the agent has civil avenues as well.