2003 Alphard Hybrid Breakdown; now won't start

Hi all, my van broke down on a freeway going up hill at high speed and under load and now won't start.  Looking for help as to what the issue could be if you have had similar experiences.

Over a 10 second period the following happened:

-going up major hill at high speed, i felt a slight loss of power

- I let off the gas pedal and re-engaged... no power response and engine mechanical sounds got much louder, then sound of a belt squeal, then a clunk that i felt in the drivetrain

- car engine stops, but continues rolling and hybrid electric system is active and tries to compensate.  Power steering is still on, brakes still work.

- I pull over.  Car wont start.  I notice that my electrical system is wonky, I can't power slide the door shut, mirrors, etc.  I believe my auxiliary battery is low.  Hazard lights work for a while.

- prior to the breakdown, no issues with the vehicle, no Check Engine Light, no warning lights that I can think of.

Key Points:

After the breakdown, my immediate thought is that my engine seized.  After being towed, all fluids good, no belts that I can see have snapped. 

The nearly dead auxiliary battery is suspicious.  Can this be related?

Boosting the vehicle has no effect;  the ready light flashes and stays flashing.  I believe I can hear the vehicle attempting to start, but it sounds very weak

I have no time to fully charge the aux battery.

Vehicle was towed to a nearby random mechanic in a small town while I took my kids home, several hundred kilometers away.  Looking for some expertise or experience regarding such issues?

Edited July 7, 20232 yr by MarkATH10W