Name of movie with woman stranded in underground garage with a deranged killer?

I saw this movie on DVD a couple years ago and it was about a woman stranded in an underground garage with a killer and no matter what it seems like she can never escape. There was one point in the movie where she was about to get away and be saved by cops but somehow the cops don't see her and turn away. If I'm not mistaken the killer turns out to be the parking attendant that works down in the garage. Please help!! I would love to see this movie again!!