2000 Ford Windstar Battery draining/lights

Electrical problem
2000 Ford Windstar Automatic 109488 miles

I parked the van yesterday around 3PM.

I returned to the van around 6PM and I noticed the rear (tail) lights were lit.

I looked in front, and the headlights were not lit.

I checked the headlight switch and it was off. The headlights were not used when the van was driven and parked.

I attempted to start the van and just got some clicks. Battery was near dead.

Now, the tail lights were off.

I returned to the van a few more hours later, and I noticed the tail lights were lit again (dimly). The headlights were not lit.

I turned the headlights on then off and depressed the brake a few times in case something was stuck, but the tail lights remained dimly lit.

At this point, the headlights were also dimly lit (presumably awaiting the turn-off delay because I turned them on then off).

I waited a couple minutes before leaving and the head/tail lights remained dimly lit.