Josh Hartnett Says He Based 'Trap' Serial Killer on People in Film Industry

Josh Hartnett took some inspiration from his real life for his recent serial killer role ... saying he based his psychopath on others he's met -- in the film industry!

The actor sat down for an interview with Entertainment Weekly Friday ... and he talks about diving into the mind of a serial killer like he did for his new movie "Trap" directed by M. Night Shyamalan .

Hartnett explains there are a lot of people on top -- CEOs, politicians and even people in entertainment -- who will say or do anything to get what they want ... regardless of the people they hurt to do it.

JH says a lack of empathy's a telltale sign for a psychopath ... and, he's met tons of people like this -- implying he's interacted with some seriously messed up people in the film industry.

This jibes with other comments Josh made recently ... admitting he bailed on the film industry partially because he was afraid fame was going to steamroll him.

Remember ... Hartnett opened up about getting stalked during a recent interview -- and those experiences made him worry H'wood would end his life, so he left before it could.

BTW ... Hartnett dug deep for his "Trap" performance -- but, critics aren't overly impressed with the finished product. The movie's got a 47% on Rotten Tomatoes though many are blaming the writing and directing rather than Josh's performance.

Bottom line ... Hartnett's research paid off -- and, actors may want to watch their back in Hollywood!!!