Blazer lost power, won't restart.
 

Hi,
I have a 1998 Blazer LT, today i was driving when the battery symbol showed on the dash, followed by all most of the electrics failing (dash, turn signals to name a couple). I've a feeling the car was just on battery power as it would not restart after it just made it home.
When I tried to jump start it the car would crank and the fuel pump seems to prime, but it will not start. Before this I was quite sure it was the alternator but surely the car would start with the jumper if this was the case? Im at a total loss to the cause.
I would really appreciate any help/advice!