Lunatic (1999)

Allen is a serial killer who one day reads about a copycat in the newspaper. Seemingly out of nowhere, he discovers her in the house of an intended victim -- it turns out he's too late, she's already done the job for him. Allen, an aloof sociopath, and Bunny, an equally twisted yet, by contrast, social individual, immediately bond and do what comes naturally: they go on a killing spree.