2004 Chevy Avalanche 5.3 V8 won't stay running now any ideas?

So I might have bought a lemon. I bought a 2004 Chevy Avalanche 5.3 V8
from a private seller. When inspecting it, I started it a couple times, and it
started right up no problem. Engine ran smooth with no noticeable
hesitations or vibrations. Test drove it and everything was fine. Shut if off
and drove it again for 2 minutes to talk to my follower in another vehicle.
Started it right back up and drove about 12 miles (25 minutes) to a friends
house and shut it off. On the way there, the vehicle drove great, good
acceleration, good idle everything. I tried to start it right back up and it
started for a split second. It turns over, you hear everything work as it
should and when it actually starts it quickly turns back off. Attempted this
multiple times (like 10) does same thing every time. After more tries I finally
got it to start and run smooth but then after about a minute or two it would
shut off. Water temp and oil temp gauges are reading normal. When it
would start to shut down I would attempt to give gas but that would not effect
it at all. One other note is the individual I bought it from said is had been
sitting for a while.
Is it possible it is just bad gas? Clogged filter? or water in the fuel?
Please help.