It's possible he was more reactive due to previous trauma, but imo there is nothing about his behaviour or demeanor in the run up to or the immediate aftermath which indicates fear. He seemed calm when walking around her car filming her, as did Renee.
Of the other two ICE agents who got out of the white car, one was perfectly calm to the point one could assume he cba and wanted to go home, and the other was angry and inflamed what was, up to that point, a relatively calm interaction with aggressive language and behaviour.
Regardless, his past trauma is irrelevant when deciding on guilt or innocence. The legal argument is "would a reasonable person," along with whether his actions were within the law if a "reasonable person" would fear for their life.
From the videos I've watched, the answer to both of those arguments is no. No other ICE agents drew their weapons, which indicates they did not fear for their lives. In fact, they seemed quite shocked when JR fired his weapon. And his behaviour was not within the law. The law, set by the Supreme Court, which cannot be overruled by individual federal organistions, clearly states that when dealing with moving vehicles, you cannot place yourself in front of the vehicle and then argue it was a threat, nor can you use lethal force to protect yourself from harm if other avenues, including moving out of the way, were available.
JR stepped in front of the vehicle. He clearly had other means of escape because less than a second after firing the first shot, he stepped to the side of the car to fire 2 more shots.
In officer-involved shootings, each shot fired has to be justified in singularity. There was no justification for the 2nd and 3rd shot, even if you could argue the first one was justified.
JRs individual trauma can be used as mitigation in sentencing, but it cannot be used when deciding guilt or innocence.
On top of this, it is JRs responsibility to ensure he informs his supervisors if his trauma is bad enough to impact his abilities to carry out his duties. If he didn't do that, it adds to his guilt, not detracts from it.