Director James Gunn has been taking to his Facebook page all week to reveal new cast members for The Belko Experiment, a project he wrote and will produce when production starts next month in Colombia, under the direction of Greg Mclean. Over the past five days, the filmmaker has revealed that John Gallagher Jr., Tony Goldwyn, Melonie Diaz, John C. McGinley and Michael Rooker will star in the horror-thriller. The director also revealed who each of these actors are playing in his Facebook posts.

The Belko Experiment centers on a group of 83 American expatriates who work in a building in Sao Paulo, Brazil, and find themselves trapped in their workplace. A voice emits over the speaker system, forcing them through a series of murderous moral decisions. Take a look at what James Gunn had to say about each of his new cast members below, and what characters they are portraying.

John Gallagher Jr. - Mike Pelk

"Well, I'm proud to announce that day is today, as John will play Mike Pelk, one of the leads of our film The Belko Experiment. The script was written by me, it's going to be directed by Greg McLean, and produced by myself and Peter Safran. I just came from a table read with John and a bunch of other talented actors, and I can't wait to get started - which we'll be doing in June in Bogota, Colombia!"

Tony Goldwyn - Barry Norris

"Tony will play Barry Norris. Norris is a guy who is used to being in charge at the Belko Building in South America, so it isn't easy for him to start taking orders when the office employees are mysteriously forced to either start killing each other or be killed. The Belko Experiment is an action-horror-thriller, but it's important to me and the director Greg McLean that it's first and foremost about characters - which is why we needed to get the best actors possible. I've been a big admirer of Tony's talent for a long time. He's an outstanding actor with an incredible pedigree, and we couldn't have asked for a better person to join myself, Greg, my fellow producer Peter Safran, and actor John Gallagher, Jr. on this journey."

Melonie Diaz - Dany Wilkins

"Have you guys seen Fruitvale Station? Well, I have, and I adored the movie. And one of the things I adored about it the most was the lead actress, Melonie Diaz. Her honest performance was exactly that kind of thing we were looking for for The Belko Experiment. So when she said she was interested in playing Dany Wilkins, one of the leads of the film, I jumped up and down and punched my desk and some trash cans and my assistant Simon with pure joy. Dany is the new girl at Belko. It's her first day working in the building, and she really couldn't have chosen a worst first day, since this is the day the employees are all forced to either kill each other or be killed."

John C. McGinley - Wendell Dukes

"I'm pleased to announce John C. McGinley has joined the cast of The Belko Experiment. I know when I think of John I often think of Bob Slydell from Office Space. Fortunately, in that film, the characters only had to murder each other spiritually, and not physically as they do in Belko. John will play Wendell Dukes, one of the top execs at Belko, and longtime friends with Tony Goldwyn's character, Barry Norris. Wendell is a bit socially awkward, and has never been at home with the other employees at Belko... I'm not sure his social problems will be eased much when mysterious forces start compelling them to kill one another or be killed."

Michael Rooker - Bud Melks

"Rooker plays Bud Melks, the head of maintenance in the Belko building. He's not a racist thug like Merle in The Walking Dead, and he doesn't have a flying arrow like Yondu in Guardians of the Galaxy - in fact, he's a pretty nice guy - so he's ill-equipped to deal with the mysterious forces who start making all of the employees in Belko start killing each other unless they want to be killed themselves."

Casting announcements will continue on Tuesday, after the Memorial Day holiday, but the filmmaker teased he may throw in a surprise over the next few days. What do you think about The Belko Experiment cast so far? Who else would you like to see join the cast?