It's listed under 'Heavy', the uses of Flamethrower and Molotov will return 'Fire'( ID: 31 ) as death reason of opponent. The Flamethrower was listed under 'Heavy' and Molotov was disallowed when we added the weapon stats( if im not wrong ), so all the count of 'Fire' whether by Molotov or Flamethrower were added to 'Heavy'.