Peter Gallagher Says Mississippi Killer Proves the Country's on 'Verge of Crazy'

Peter Gallagher says the U.S. is "on the verge of crazy" in light of the Mississippi shooting that left 8 dead this weekend ... but he has hope for the country.

We got the "Law & Order" actor Sunday at LAX, where we asked for his thoughts on the man who went on a shooting spree in Mississippi, killing 8 people ... including a sheriff's deputy.

Peter tells us straight up ... the country is in a weird place at the moment, all things considered.

But as far as what should be done with this new alleged killer ... he says he has faith in the criminal justice system ... and the country as a whole.