The actor plays a police officer in new drama End of Watch and he went through some intense training for role, including patrolling the mean streets of South Central Los Angeles with local cops.
He also agreed to be subjected to a shot from a Taser gun to gain first-hand experience of how the weapon works, but he regretted his decision.
Gyllenhaal tells U.K. talk show host Graham Norton, ""The police offered us the chance to either be pepper sprayed or Tasered. We are actors and not the sharpest tools in the shed so we decided to go for quick and painful rather than long and painful.
""I was an idiot and there was no logical explanation why we did it but I think experiencing things does influence the realism in the movie. It felt terrible. They said they would do it for five seconds and I was screaming like a child pretty quickly. It felt like it was forever and it lasted a second and a half!""