When this proves impossible, and a gun is trivially easy to obtain, what do you think happens? The president-elect himself is alive today only because a bullet was off-trajectory by a centimeter or two.
It remains to be seen whether this will be allowed. The jury may be unable to agree that this person should be found guilty despite the video evidence.
But, I also understand why this happened and frankly don't feel to aggrieved by the death of this CEO.
The issue with US politics is that no law is forthcoming to address anything that happened. We won't see silencers banned or gun control laws enacted. We certainly won't see regulations on health industry to stop them from bleeding leukemia patients of every cent they own.
So, I'm apathetic. If some of these CEOs are going to die as a result of their greed and the lack of justice against the wealthy, so be it.
But the purpose of courts is to substitute for private vengeance. If they are not willing to do so, this doesn't mean that you have a right to just roll over and die.
If a court says they will not hear you because the person who killed or severely harmed somebody has immunity, or because it has made itself some rule that it feels prevents it from hearing your complaint, then it has made itself irrelevant.
The fact that there's so little sympathy for the death of a CEO who, in their view, callously discards human life tells us the authority is a much smaller dealbreaker than the justification.
On the contrary, it's the crucial distinction. Without process and authority we have mob violence, vengeance killing, and vigilantism. Lynching, clan blood feuds, gang violence, all proceed from this same theory that "getting back" is more important than following the rules. In that world, Brian Thompson's killer should expect to be shot by one of his children for taking away their father.