my car failed me this morning, I am trying to narrow down what is wrong.

I was driving, about 3 mins away from home and all of a sudden the engine cuts out and would not start anymore. MB roadside assistance was not able to jumpstart with a battery pack nor a fresh battery.

Could the alternator be damaged from a v belt that is too tight or a smog pump pulley that is broken? right now the car is cranking very slowly, even with the fresh battery and battery pack.