Truck went from working perfectly to unable to start in 1 second while traveling at 70 mph on the interstate.

My very dependable 2001 Chevy Suburban LS with 165,000 miles was working perfectly on cruise control at 70 mph on the interstate going east from Houston toward Louisiana. Then, I noticed that I was losing speed, and I could see from the lights on the dash that the engine had shut off while the truck was still in gear. I coasted to a stop on the side of the interstate, shifted into park and tried to restart. I noticed that the engine turned over more rapidly than usual and would run very roughly for a second or two, but no longer. I had to get towed in to a Chevy dealer and am waiting to see what they find out after the Labor Day holiday. So what could make the truck just shut down like that without any warning? I am dying to hear your theories! Best, George Paul