James Gunn has opened up on all the emotional challenges he faced whilst filming 'The Suicide Squad'.

James Gunn (c) Instagram

James Gunn (c) Instagram

The 'Guardians of the Galaxy' director began production on the sequel to the 2016 DC Extended Universe movie last year with Margot Robbie, Joel Kinnaman and Jai Courtney reprising their roles alongside newcomers John Cena, Idris Elba and Taika Waititi.

The 53-year-old filmmaker marked the end of filming with a touching post on Instagram in which he revealed that he had a hard time helming the movie as he was grieving the loss of his father and his pet dog.

Alongside a snap of the entire cast and crew, he wrote: "And that's a wrap on #TheSuicideSquad.

"My father died two weeks before we started filming and my dog died two weeks before we started filming and my dog died two weeks before the end. It was a hard, hard time in my life and yet the most fulfilling time I've ever had making a movie."

Gunn also paid tribute to the project's star-studded cast, which also includes former 'Doctor Who' star Peter Capaldi, Pete Davidson, Nathan Fillion and Michael Rooker in mysterious roles.

He posted: "The professionalism, talent, compassion and kindness of this cast and crew inspired me every day. Thanks to everyone involved in this film, in every stage of development, in every department - I am grateful from the bottom of my heart to you all. You are why I make movies."

Fillion, 48, recently praised Gunn as "an amazing storyteller" and revealed that he didn't hesitate when offered a part in the film.

He told ET Canada: "James Gunn, one of the people in my life that when he calls I just say 'Yes to whatever you're about to say. It's yes, the answer's yes.'

"James Gunn is an amazing storyteller. That guy understands a story, and he loves to tell a story.

"So when he wants to do something you know it's gonna be fun, you know it's gonna be satisfying."

'The Suicide Squad' is set to hit cinemas in August 2021.