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.
The Stanford Prison Experiment is a good analogue to what we are seeing with ICE. People empowered to be cruel.
And they are given the message (from the president!) they have absolute immunity, and instructed to regard the law as a set of nonbinding guidelines.
The Supreme Court played a role in this too. They made it harder to stop by halting the long-established precedent of nationwide injunctions.
The people pulling the trigger are still not blameless. They are murderers no matter how badly misled. Your common murderer is misguided too. That doesn't mean they are absolved. I don't think that's what you were saying, but it bears mentioning.
I personally don't think it's making the agents worse, but rather that it's very heavily selecting for very bad people. If you have a job where people can be violent and abusive with little-to-no oversight, you are going to select for people who want to do violent and abusive things. Keep in mind, these people aren't being "drafted" into ICE, they're voluntarily joining, meaning that they had to demonstrate some interest in it.
This doesn't imply that every ICE agent is a terrible person, just like how not every Catholic priest abuses children, but if you create a selection pressure then it isn't surprising when you get what you selected for.
Sample size of one but bear with me; I am an asshole but I am a decidedly non-violent person. I genuinely do not want to commit any form of violence on people. Law enforcement doesn't seem appealing to me because it pays worse than software and I wouldn't view physically attacking people with impunity as a benefit.
ICE is said to be paying signing bonuses up to $50,000 [1]. That must seem like a fortune to the sorts of people they are recruiting... people who would happily do stuff like this for free if given permission.