2012 Regal GS Not Starting... making awful noise

[mattoco7]

Ok so I picked up a 2012 gs with the 6MT about two weeks ago. The car had 67k on it, and drove great on the test drive and for the last two weeks. Last night however I was driving home and getting into it a little (80-90 mph or so,) and the tachometer went to zero. The car was driving fine, so I drove it another half mile or so to get it home.

I parked the car, turned everything off and then tried to start it again (hoping the tachometer would reset.) The car won’t start. Making a knocking noise when it tries. Had towed to dealership immediately. Any ideas on what could be going on?