Jake Gyllenhaal thought filming 'End of Watch' was traumatic.
The 31-year-old heartthrob experienced scenes of extreme violence while preparing for David Ayer's harrowing new cop drama as well as undergoing five months of intense preparation on patrol with real Los Angeles policemen.
He told the Telegraph newspaper: "Once, outside a motorcycle club, a large man had been shot up. He had about 10 bullets in him, but was cognisant and talking.
"We saw a lot of stuff, a lot of violence, and without a doubt this has had more of an impact on me on than anything I have done before."
The 'Donnie Darko' star confessed working with writer-director David - a former LA gang member - was life-changing and says he now understands the post-traumatic stress that police officers suffer from.
Jake explained: "It's changed things for me in so many ways, not least in how I regard the police. People talk about post-traumatic stress with soldiers coming back form war, but no one thinks about cops on patrol and what they deal with. I had no idea what these guys, or their spouses, go through.
"And also, on a personal level, making the movie transformed my view of Los Angeles. It made me fall in love with the place again."