2004 Hyundai Elantra electrical on the fritz

On the hottest day of the year, after about 10 minutes of driving, several things in my 2004 Elantra GT started malfunctioning:

1) the radio got static-y and then just stopped all together and wouldn't power back on.
2) the air bag light started flashing erratically
3) the car wouldn't accelerate quickly and sounded weird and sluggish at low speeds.
4) the windows in the back rolled up sluggishly and the front driver window would not roll up at all (after I turned off the air conditioner --which seemed to be working fine)
5) upon getting out of the car, the two chimes that ring when the door is opened in a "ring-ding, ring-ding" fashion would only go: "ring, ring, ring". Without the second toned "ding".

What is the suspect?