I think it's more likely that that ICE agent was trigger happy, as the woman was initially responding to the people approaching her from her left and was clearly reversing and then steering towards the right to drive away. The agent then fires two additional rounds through the side window when any "threat to his life" (ie. the direction the vehicle was then heading) is no longer a relevant factor.
Side-stepping and/or utilizing non-lethal means given that it appears the driver's window was down would have been much more prudent options. Even if accepting your premise entirely, the 2 additional shots make no sense.
I think the main thing is that police do not have the duty to retreat. For example, if someone draws a knife and runs toward an officer, he has the right to shoot him, even if the officer has the ability to run away instead. The woman was commanded to get out of the vehicle (which *is* a deadly weapon, this is akin to being commanded to drop the knife). She refused this command and actuated the weapon. It is clear to me that the shots weren't absolutely necessary but he was in his right to fire. Police are not obligated to use less-than-lethal measures in situations like this - you could argue they should be, but by law they aren't obligated.
Refusing to cooperate with police can turn deadly fast. It's an entirely avoidable tragedy if she merely stopped the vehicle and got out.