Well, since this IS a hypothetical senario....
Make sure there are no witnesses around...
Put on gloves...
Using the shotgun, shoot the idiot...
Recover your spent shells...
Set the dog free...
Use the remaining gas and the lighter to burn the guys body and the gloves...
Get back on the road again...
Clean shotgun and dispose of it, along with the spent shells and the unspent ones, in the next county or state.
Make sure there are no witnesses around...
Put on gloves...
Using the shotgun, shoot the idiot...
Recover your spent shells...
Set the dog free...
Use the remaining gas and the lighter to burn the guys body and the gloves...
Get back on the road again...
Clean shotgun and dispose of it, along with the spent shells and the unspent ones, in the next county or state.