` cannibal cop ' gilberto valle stars in an hbo documentary called thought crimes which premiered on thursday at the tribeca film festival .
` when you 're behind a computer screen late at night , no one knows who you are , where you are , ' valle says in the opening of the documentary .
valle insists throughout the film that he never intended to actually hurt anyone and says he just has dark fantasies .
valle was arrested in 2012 for plotting to kill and cook women but was released in july .