3 loud beeps, no lights, shut off won't start

I was driving my 02 golf tdi and heard 3 loud beeps with no dash lights or anything at all. 2 days later the car was running and in neutral when it suddenly shut off, lost all power, can't even roll up windows, dash won't light up. Completely dead. Any ideas?

If you boost it , does it start/power up? If so you have a bad battery or alternator. Or bad wire going to the alternator. When the regulator isn't sending a signal back the charging light wont come on.

Have to do a full troubleshoot of the electrical system. I suspect that alternator (at least the regulator) has gone T-up. Check to see if there's any seizure of the alternator (check belt- comprehensive check would be to remove the belt and then check all the pulleys).