Revealing mistake: When George Clooney is talking to Juliette Lewis towards the end of the film, it is painfully obvious that his tattoo has been smudged. (01:40:35)
Continuity mistake: During Santanico Pandemonium's routine, two dancers take the snake away so she can step forward. As they take the snake off, the second dancer is holding only a couple feet of the snake's tail, but in the next shot, the second dancer is holding the entire snake. (00:55:40)
Continuity mistake: In the hotel when the manager comes through the door, in the first shot the door is open, but the next time the door is closed.
Continuity mistake: Frost gets green blood all over his hand after holding the vampires heart, but this disappears while they are fighting the four women. After the fight finishes, the blood returns.
Continuity mistake: When Seth introduces Gloria to Mr. .44, the gun is level and pointed at the door. Cut to over Seth's shoulder and the gun is pointed at the ceiling. (00:14:55)
Continuity mistake: As Santanico Pandemonium begins her dance, she tosses her cloak off and a stage hand emerges to remove it almost immediately. The stage hand then disappears in two shots of Santanico onstage, then reappears folding the cloak. (00:55:00)
Continuity mistake: In the opening scene, the pages change in the magazine that the convenience store clerk is reading. (00:01:30)
Continuity mistake: The scene where the vampires in the Titty Twister bar start devouring the customers. George Clooney confronts Salma Hayek. She taunts him and he shoots her. When he does this the jacket falls open to show he is wearing a white shirt underneath. However, when she comes back to life a couple of seconds later and punches him to the ground, his jacket falls open again - only this time it is a completely black shirt underneath.
Answer: Because he is a sadistic lunatic and he wanted to. He has a lot wrong with his brain, paranoia, psychopathy, hallucinations, sexual predation. Probably more. He is a deeply disturbed individual and killing Gloria gave him pleasure.
lionhead