That said, universal background checks are a simple and straightforward approach. The seller and buyer get together and fill out a state form (2 copies). Once that is done, the seller calls the phone number and reports everything on the form to the operator, who enters it and runs the NICS check. If it comes back clean, an approval number is given and logged on each form. The buyer and seller then sign the forms and each keeps a copy. We have this in Connecticut.

it should expire every few years like a driving license. Yearly would be even better. At which time, a new background and mental health check should be completed.

And it should apply to police officers too.

If your drivers license expires, you don't have to give up your car. It's still your property and you can keep it at your house. You just can't operate it on public roadways. For firearms, the analog is Concealed Carry permits or hunting licenses. If they are expired or revoked, they can't carry or hunt, but the guns still remain in their possession.

There are no legal methods to change that under US law. The only method to remove guns is through due process in the courts, and that requires some sort of crime or the like to be committed.

I described how CT does it in post #3. It just takes political will.

What makes them dangerous? Is Chief Mina once again talking about Wayne LaPierre's monsters among us?

As seen in New York, pushes to identify more dangerous people can have questionable results. The SAFE ACT, compelling the mental health industry to report 'dangerous people' to a criminal database quickly led to hyper-inflation in reporting. The rate of reporting mentally ill persons as dangerous in New York is now multiple times greater than the historic rates of actual adjudications of dangerousness.

It remains to be seen just how dubious a value this criminalization of mental illness will be for New York. But analysis of the FBI NICS database suggests persons adjudicated dangerous by reason of mental illness are not only fewer in number but also have a much lower rate of being caught attempting to buy firearms (catching people thusly is the entire justification for the background checks) than persons with various criminal records and association with illicit behaviors...particularly drug use.