Yeah, I enjoyed that!
The controls felt good (I didn't have the control lag issues), the shotgun felt powerful, the long reload had me scrambling for cover. I'd add more enemy types though. Maybe a ghost that attacks from super close distance? Right now the tactic was to just keep the distance. Also, I have a hint when it comes to writing enemy AI- set the walk target near the player (but not exactly on player position), and change it randomly every few seconds. This makes the enemies move in a manner that's hard to predict, but still focused on the player.
The graphics were ok, but I really enjoyed the player's animation. The fact you made sprites for every aim direction- that's extra effort, but it makes your game look more cool!
The sound was ok. Shotgun sounded good, the rest was all right.
As for the use of the theme... THIS TIME, IT'S YOU WHO HAUNTS THE GHOSTS!
Seriously though, I had lots of fun, keep it up!