warning lights on while key is out of car

My dad has a 1992 Regency Elite that has a major problem. While the key is out of the ignition the waring lights are on and the warning buzzer sounds.

The car was running fine on the interstate last week. As he pulled off at his exit, the car died and the warning light came on and the buzzer started to sound. Now the car just cranks but will not start.
Here is a list of the problems he is having.

Will not start
Horn, headlights, power windows will not work with or without key
No fuel pressure
Low coolant, low fuel, hot light, buzzer are on while key is out of the ignition
Turn the ignition key on and the buzzer stops and the warning lights go out

Is the ignition switch a good place to start looking? Somebody thought the alternator shorted out but we disconnected it and it didn't change anything. We checked all fuses and they are good. Any suggestions.

Thanks!!

Let's start by checking all the battery cables & connections. Disconnect all the cables, remove the bolts & the rubber boots. Clean off any corrosion with sandpaper or wire brush. Apply some dielectric grease & reassemble. This is a very common problem, let us know what you find.

I'd agree with Mickey on the cables.
Wouldnt hurt to test the voltage with a voltmeter too.

Should be around 13 vlts, 14.5 or so when the engine is running and your charging system is functioning properly.