1999 Dodge Caravan won't start after making a "zipper&q

Traveling down the freeway yesterday, doing about 70, I heard a strange sound like a zipper from the engine. I took my foot off of the accelerator and the sound stopped but the engine was weaker. A few minutes later it made the zipper sound again and again the sound stopped. I pulled over and the engine cut out as I was slowing down. Turning on the ignition the engine cranks and eventually sputters to a very brief and weak life but will not remain running and builds up pressure/backfire blowing the rubber hose off of the top of the valve cover.

I am thinking timing belt failure, otherwise I'm at a loss. Any ideas?

Vehicle is a 1999 Dodge Caravan Sport, 3.3L V6 Flex Fuel with 142,000 miles.