first, i have to agree that this kid is lucky the shooter wasnt better with his weapon... that said, its too bad this happened...

you never know til you're in the situation but this is what i imagine i would do:
give the intruder about .1 seconds to gtfo (assuming he was still in/near my door, if he is actually in my house, all bets are off)
shoot til he hits the floor
if he still happens to be alive with a load of 00 buck shot in his chest, i would probably stand over him, muzzle to the head until the police got there...

one thing i can be certain about, the homeowner in this situation checked to see wtf was going on BEFORE getting his gun.... id get the gun first and then check and see who is coming into my house. what happens if the intruder is a threat, you might not have time to arm yourself.