2000 Chevy Blazer Vehicle died and won't turn over

Ok so the problem with my blazer is the battery light was on for a while, thought nothing of it till the weekend but when I was on my way to work it started losing a lot of power, everything turned off lights, dash board, everything in the vehicle, by the time I got to work the Blazer would barely drive, made a "chugging" sound and after I shut it off it wouldn't start again. I got it towed home and later on that night when I checked it all the lights and stuff would come on but it wouldn't turn over not even a little bit, I'm wondering what this could possibly be, I am thinking alternator but I am just wondering if there is a more definate way to tell, because I thought it would be able to start off the battery at least for a minute if it was the alternator, but I can't even get a tiny little bit of a crank
Please Help
thank you