"Everyone is upset for the cast and the crew, but there was always a feeling that something was going to happen," a source tells PEOPLE

As ABC considers the possibility of a Roseanne reboot, the cast is still reeling over the series’ cancellation this week.

“The cast all loved each other. It was a really happy family on set and everyone was so excited to be working together again after all those years, including Roseanne,” an insider tells PEOPLE about the sitcom, which was canceled on Tuesday after its star and creator, Roseanne Barr, posted a racist tweet about former Barack Obama senior adviser, Valerie Jarrett.

“So for this to happen is all the more upsetting,” the insider adds.

A source at ABC calls the situation “really unfortunate” as the revival was the network’s “biggest hit.”

“Everyone is upset for the cast and the crew, but there was always a feeling that something was going to happen. There was always a heightened awareness with her and we were always on edge about her going off track,” says the source.

The ABC source adds, “But you just hold your breath until it does. Did we think she would say something like that? No. But then it all fell apart.”

Barr, 65, prompted the cancellation of her show earlier this week when she likened Jarrett to an “ape” in a since-deleted tweet. She has since claimed that she didn’t know Jarrett is black — and that she was on Ambien while tweeting.

The star apologized to the “wonderful writers (all liberal) and talented actors who lost their jobs on my show due to my stupid tweet,” and she also expressed her regret over two costars in particular: John Goodman and Laurie Metcalf.

“I just wish ABC had not thrown two of the greatest actors in the world out with me — Laurie and John,” Barr tweeted Wednesday night. “I’m so sick over this — they will never have better character actors on their network.”

Although Roseanne won’t be returning to airwaves, a possible spinoff could be on the horizon.

A source close to the project confirms to PEOPLE that there are discussions underway about a potential reboot revolving more around Sara Gilbert’s character, Darlene Conner.

“Talks are underway, but it’s too preliminary to know if it’s going to gel or not,” says the source.

Days after the network scrapped the show, Barr tweeted Thursday that she “begged Ben Sherwood at ABC 2 let me apologize & make amends,” referencing the Disney/ABC Television Group president.

“I begged them not to cancel the show. I told them I was willing to do anything & asked 4 help in making things right,” she continued. “I’d worked doing publicity4 them 4free for weeks, traveling, thru bronchitis. I begged4 ppls jobs.”

She added, “He said: what were you thinking when you did this? I said: I thought she was white, she looks like my family! He scoffed & said: ‘what u have done is egregious, and unforgivable.’ I begged 4 my crews jobs. Will I ever recover from this pain? omg.”