I saw this many years ago on a flight from ORD-DFW. There were 4-5 "men in black" suits and probably 1/2 a dozen handcuffed men all carrying shoe boxes in front of them. I got pretty freaked out. They put them all in the last several rows of the plane. You could plainly see the suits all had guns on them. I avoided the back galley/bathrooms on that flight.