Why won't my 1999 chev trailblazer drive or reverse when I shift gears?

What is your question?

Vehicle was running just fine. I parked it. Approximately 1 hour.later I put key in ignition and started my vehicle with my foot on the brake and put it into drive and a loud bang sounded and then a grinding noise like I was dragging cement.

What makes this problem better or worse?

There were no warning signs

How long has your 2002 Chevrolet Trailblazer had this problem?

It was immediate with no warning