There are plenty of dangerous mentally ill people out there who don't use any type of logic or reason as a basis for their decision-making.
The shooter is also in custody already and captured thankfully.
The first person of interest was detained, but released.
FBI director says a suspect is in custody. That governor says a person of interest is in custody. Local police say the shooter is still at large. This is what Reuters was reporting as of 1 hour ago.
People decide to kill people all the time. People order others to kill people all the time. People advocate for others to order yet others to kill people all the time. Some violence is legitimate. Some violence is justified. Plenty of violence is neither. But to ignore the violence of the state as sanctified, while condemning all violence against it as madness results in an alarming ethical framework with abhorrent conclusions.
I think that's the mixup. You can be insane but still perform some very calculated plots.
Mental illness isn’t the only explanation. When people are indoctrinated into stupidity and no longer believe in truth or reality, it’s possible to convince them to both believe “I support police / military” while attacking police officers (several of the worst offenders of Jan 6).
Perceived desperation is a better explainer than some generic mental illness.
Also, I would argue that it has more to do with mental framing than “being crazy”. Police and military leadership hire selectively and craft training to ensure that people aren’t mentally ill and still willing to kill.