While this might seem like retarded logic you are failing to see the hidden truth behind it... he understands he needs to get a gun so he used what he had available in an attempt to take possession of a superior weapon. Clearly his execution of said mission was lackluster, but good for this criminal. He aspired to obtain a better tool for his criminal endeavors. :)

Personally I think I would have found a house I knew(or it was at least highly likely) had guns and robbed it when no one was home. No one ever said your average criminal was overly smart.