My heart aches for the countless victims of this band of fascists in the executive branch.
I think they are simply poorly trained people that are given free reign. The results are disastrous. They probably don't wake up thinking "Today I'm going to murder someone" but they just don't realize what they're doing. I'm not sure how it's at the destructiveness scale at this moment, but these organizations can and it probably will get much worse as their internal culture morphs into more directly aggressive stance.
The shootings were incredibly dumb, and it's pretty much what one would expect when they create this kind of situation. Listening to the "Revolutions" podcast I realized situations like these are incredibly common all along history, you have armed people with tense spirits, a gun goes off and tragedy ensues. The most terrible part of all of this is the reaction of the authorities that lie, gaslight and support these people, get them off the hook and this reaction will only generate more violence and more deaths as ICE realizes they _really can_ act with impunity.
Obviously, the ICE agents have to rationalise what they do. "We are the good guy, we work against the bad guys". But I don't think that they wake up in the morning hoping that they will have an opportunity to hurt what they themselves consider "average americans".
Looking at the video, I could totally imagine that the first shot fired was a mistake, and then one or more of the agents panic and shoot... well... a LOT of times. That doesn't seem rational, or professional. I don't think that the agent thinks "ahah! Here is my opportunity, I'll shoot him 5 more times". Still, they killed someone for no apparent reason (it's not a proportional defense, quite obviously) and they should be judged for that.