2001 Chevy Blazer no battery power after charge

I unlocked my vehicle with remote, the doors open, I put the key in, I heard something, then got no power. I got a booster pack to jump it, to no avail, someone hooked their car up with cables, we let it sit, still nothing. When the booster was connected, the tech was moving something near the battery around and for a second my flashers came on and I had power, tried to turn the car on but the power was lost.