ignition will not turn
 

I own a 2000 Cadillac Deville base. I left my headlights on at wrk. When it was time for me to leave the car wld not start jst a ticking noise. Tried to start engine a second time wld not start afterwards, I believe security system shut on and locked the ignition. I had to turn the ignition hard to put bck in off position engine did not start either. I believe the headlights drained the battery because the door lock buttons were no longer operational as well as key fob. Today went bck to wrk and now key fob wrks as well as hazards and door locks. The ignition was still locked cld not turn ignition at all. I turned headlights on and car went totally dead. Does this sound like dead battery issue also owners manual says to to locate Console shift release lock and hold down while turning ignition, where the shift release lock located? Manual says it is on center console, i don't think I see it.