Richard Harmon revealed the fun behind playing a “psycho killer” while working with Gary Cole and Shawn Ashmore on the new movie Darkness Falls.

The film follows Detective Jeff Anderson (Ashmore), who begins investigating his wife’s suicide because he suspects she has actually been murdered. He finds that a father-and-son team (Cole and Harmon) has been murdering famous women and so he sets out to stop them.

Harmon calls his character “a bit of a slippery one.”

“I play a character named Adam, and I had the real luck to be able to play Gary Cole’s son, which to me as soon as I found out who was playing the father of me I was so excited I’ve always been a fan of Gary Cole for a long, long time.

“So we are a father and son serial killer duo, and we, in my mind, it’s sort of like we represent this kind of toxic masculinity between the two of us, and that my dad raised me to have this real issue with successful women,” said Harmon.

“He’s sort of this [killing] machine, but the thing with him is that if ever my father is not there to make the orders and make the calls, my character kind of reverts back into being a little bit of a lost child who doesn’t know how to make decisions on his own, then he gets a little aggressive, he gets a little angry, and he kind of throws some tantrums. And he’s very much — you don’t know what to expect from him.

“He was fun, a lot of fun to play,” Harmon said.

The actor said that his co-stars were “brilliantly professional in their own different way.” He mentioned that Ashmore, and the director Julien Seri, were always down to “play” and “switch it up.” And said that his goal on set was to make Cole laugh.

“Standing on a driveway, and I started singing “Psycho Killer Qu’est-ce que c’est” that song,” started Harmon. “And I started singing it, and then very quietly Gary started singing it beside me, until we were both just singing “Psycho Killer Qu’est-ce que c’est” playing psycho killers.”

And finally, his favorite scene to shoot?

“Again, without giving anything away there is a scene very near to the climax of the film that Julien had a brilliant idea, it’s a huge scene, and he thought, why don’t we just do it in one, one shot,” the actor said. “Which to me reading that scene I didn’t know how that was quite going to be possible to be done, but he mapped out the whole thing.”

Darkness Falls was released June 12 and is available to rent on Video on Demand and Amazon Prime Video. Check out the trailer below: