From his perspective and in the time he had to assess and react, he could reasonably perceive that to be the case.
I'll add to my earlier comments on this that we often have expert witnesses who study reaction times. The officer must assess the situation, decide to fire, then physically fire. Then, as circumstances change, he must reassess the situation, decide to stop firing, and then physically stop. Each direction takes in most studies a tad over 2 seconds.
In this case, that allowance for his reaction time is well within reason.
While I agree with criticism of ICE being there at all, and am critical of the administration for doing this, and while I agree that Trump, Noem's, and Vance's attacks on this lady are reprehensible and stupid, as to the actions of the officer -- completely lawful. Unfortunate, but not unlawful.