Hiram was a monster even before he was transformed into a giant octopus. He killed his wife and her Lawyer, fired his employee's, stole their pension funds and foreclosed on their mortgages, leaving his employees broke and homeless. He did most of this to finance his son's research into making monsters. When Azrael investigated the monsters showing up in websterville he was turned into a giant octopus as a last resort by his son.
Hiram uses a .45 pistol.
Hiram's supreme greed was his main weakness.