Avalea

After the cut scene with the alligator, turn around really quick and run away from it, until you get far down the hall.

To the left of the screen you'll see a capsule embedded in the wall, and there should be a light above it, run over to it and select it, and it will ack if you want to release the capsule, obviously select 'yes'.

Then back up just a little and raise your gun (any gun you choose). Wait for the croc to come forward a ways and he will pick up the can and hold it in his mouth.

Shoot forward a couple of times and the bullet will eventually hit the can and it will make the alligator explode.

Ta-da!
:)
Easiest boss in the game if you ask me lol.
Avalea