If this happened without any sign, just suddenly dead, then it is most likely from the assembly. If you noticed the window worked slower for sometime, then the motor is gone. You need to replace the motor. You can buy it from the Pepboy (much cheaper than the Dealer,and more powerful).

Note:
You should never push more than one button to open or close window(s). That would
draw more current from the battery and the battery voltage will be low for that.
Then overheat will be produced in the motor, and eventually, the motor refuses to cooperate.

Good luck and God bless,