electrical system malfunction

I drove home from work with no issues, then went to start the car about 30 min later and it wouldn't start. The brake pedal extended and locked, as did the wheel. I tried everything I could think of to get it to start (including the "emergency start" by putting the key fob into the start button) but nothing would work. The start button was blinking an amber color so I thought it was the key fob battery. Ran to the store, in another car, and got new batteries, but it still wouldn't turn on. Tried disconnecting and reconnecting the battery, but nothing happened. Finally, after about 2 hours trying to get it to start it randomly started. However every light on the dash was lit up like a Christmas tree, with indicators and symbols I'd never even seen before. Put the car into drive, to move out on to the street, and turned on the bright lights and the car immediately powered down. Turned it back on, turned the brights on, and it did the same thing. Turned it back on and moved it without the brights and left it until morning. Went out the next morning, and it started, but it was beeping a very loud "warning" type beep. Started driving, turned on the left blinker and it powered down. Turned it back on. Got on the interstate. Drove at what I perceived was my usual speed, but the speedometer registered "0 mph". All dash lights still on and beeping sound still going. My car got cut off on the drive so I went to honk the horn - no sound came out, but it did turn the infotainment system off. Tried to honk the horn again and it turned the infotainment system back on. Went straight to a mechanic. Tried to park the car and turn off but it wouldn't turn off. Advised the mechanic to turn the brights on, which did turn it off. Was told the next day that they had no idea what to do. Went to go pick it up that evening. It started, but everything else was the same - all dash lights on, still beeping loudly, start button still blinking amber color, blinker and bright lights still turning the car off. Also noticed that one head light and one tail light are now out. Got it back home and turned it off via the bright lights. When getting out of the car I noticed that all of the accessory functions and lights were on, despite the car being off. Turned it on and back off again. Accessory lights still on. Started it back up ad turned on the auto headlights, which then turned all the accessory functions off. But then the headlights wouldn't turn off. Finally just disconnected the battery again and went inside. I'm told that the Mazda service center won't be open for 2 more days. I wonder what new issue I'll discover when I try to start it today ...