Keeping Up With the Kardashians returned with an explosive episode last week -- during the season 18 premiere -- after tensions boiled over between Kim Kardashian West and her sister, Kourtney Kardashian.

In the closing moments of the show last Thursday, an exchange of words escalated into a full-blown slap fight between the siblings, and the altercation apparently came as a real shock to their mom, Kris Jenner.

Kim joined Jimmy Fallon on Monday, via video chat, for his first televised episode of The Tonight Show: Home Edition, and the reality star reflected on the uniquely brutal interaction.

"When my mom saw that, a clip of that, she cried," Kim recalled. "She was like, 'What is going on? Who are you guys?"

The fight -- which came after several seasons of mounting drama and tension between Kim and Kourtney over the latter's growing disillusionment with being on KUWTK -- really blew up when Kourtney pushed Kim over and subsequently dug her nails into Kim's arms and back.

"It was intense," Kim said of the confrontation. "I don't really ever resort to violence like that. But she scratched me so hard, you couldn't see, but I was bleeding. And so you didn't really get see that detail [on the show]."

"When I looked down at my arm and saw she had had really scratched me and I felt it on my back, I just, you know, went over and slapped her back," she added. "It's not like my proudest moment but we were going through it."

According to Kim, that kind of truly physical fighting and angry drama is "not really what we do."

"We shut down production for a week after that," she shared. "Everyone was really shook for a minute and just was like, 'This isn't like our type of show.' We want everyone to be comfortable and safe."

Kim went on to say that she and Kourtney are "obviously" fine now, and explained that her sister, has "made the decision to take time off now."

"I think she really needs it," she added. "I think that will be so much better for her."

While Kim painted their relationship in an amicable light, Kourtney took to Twitter during Thursday's premiere, and seemed to present a much less cheerful image of her depature from their show and their altercation.

"When one fan called the fight "very cringe-worthy," Kourtney retweeted the sentiment, writing, "It's trash #KUWTK."

The mother of three then seemed to confirm that she had quit the show in multiple replies to fans.

When one commenter wrote, "@kourtneykardash just needs to quit the damn show! I’m over her not wanting to film. #KUWTK," Kourtney replied, "I did. Bye."

One fan mentioned that Kourtney's sisters don't seem to apologize or correct their tone when she expresses her frustrations with them, to which Kourtney responded, "Never. They actually don’t see where my hurt comes from."

Kourtney also tweeted, in regards to comments about her decision to quit, "Took a lot to get there but choose happiness always. It’s easy to forget what really matters."

Check out the video below for a look at the sibling showdown.

Keeping Up With the Kardashians airs Thursdays at 8 p.m. ET/PT on E!

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