Kim Kardashian's fight with her sister Kourtney Kardashian on their reality series went viral -- and even though many viewers doubted the authenticity of the fight, Kim insists it was real.

Speaking on Tonight With Jimmy Fallon, Kim says that production for the show was shut down for a week and that her mother, Kris Jenner cried after the fight.

"It was pretty intense. I feel like it's been a lot of built up resent from Kourtney, or just feeling g like she doesn't want to film anymore. She's not the type of person to make a decision and say 'Hey guys, I'm not gonna film.' But she would come to work with an attitude every day, and kind of take it out on everyone from the crew to us, and wouldn't really make that decision. So we would kind of like just keep on pushing her to figure out why she was so unhappy," Kim explained.

"Kourtney and I obviously are fine now, but we shut down production for a week after that. I think everyone was shook for a minute. Like 'This isn't our type of show, what's happening.' We want everyone to be comfortable and safe. And so, you know, that happened. I don't really ever resort to violence like that, but she scratched me so hard, which you guys didn't see. I was bleeding, and so you didn't really get to see that detail. But when I look down at my arm and I saw that she had really scratched me and I felt it all on my back, I just went and slapped her back."

Kourtney is taking a break from the show as well.