Every Boss Fight made easy.

[II Mortis II]

I've had this game for a while now but I haven't got very far at all. Reason being I bought it at the same time as a couple of other games, got to the first boss in DE and lost the fight, decided to play one of the other new games I bought and just sorta lost touch with DE. Now I've decided to come back to it and I start just before entering this boss fight. I have next to no ammo and I can only find 1 room with a little bit of ammo in it.
I'm thinking there is no way around this issue, so I need suggestions... should I re-start the game from the beginning? Is there an easy way of beating this dude with the equipment provided in his room?