Erin Moran's TV Brother Ron Howard Had No Idea She Was Ill, Says Her Death 'Really Did Hit Hard'

Authorities say Erin Moran, who died on Saturday, likely succumbed to stage 4 cancer

Erin Moran‘s cancer battle came as a surprise to many — including her former costar Ron Howard.

During an appearance on Monday’s episode of The Talk, Howard admitted he wasn’t aware that Moran, who died Saturday at age 56 after succumbing to stage 4 cancer, was sick.

“It’s been a rough time,” said Howard, 63, who played Moran’s onscreen brother Richie Cunningham on the beloved sitcom Happy Days throughout the 1970s and ’80s. “My stepmother Judy passed away a couple of months ago, so the Erin event really did hit hard. … I had no idea she was ill whatsoever.”

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Howard also reminisced about the late actress, calling her a “great, irrepressible spirit and a wonderful talent.”

“She was always the kid on the set, in a way,” he recalled. “When I think of her then, which is how I choose to think of her, she was this feisty, spirited little girl.”

“It was kind of a boys club, we had all the guys goofing around … a lot of hijinks and goofy frat stuff going on,” he said of his years on the Happy Days set. “But I do remember a particular moment — we were in rehearsal, in our rehearsal clothes, and it was kind of turning into a shaving scream fight. And she did sneak up behind Henry Winkler with a pretty good shaving cream pie, and she got him.”

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Moran, best known for her role as Joanie Cunningham on the popular series, died on Saturday in rural New Salisbury, Indiana. The actress passed away in the weathered, gray trailer she shared with her mother-in-law and her second husband Steve Fleischmann, who is a Walmart employee.

On Monday, a statement released by the Harrison County Coroner’s office revealed that Moran “likely succumbed to complications of stage 4 cancer.”

“Standard toxicology tests were performed and the results are pending,” continued the statement. “However no illegal narcotics were found at the residence.”

PEOPLE has confirmed through a law enforcement source that Moran was receiving treatment for her stage 4 cancer, including being fed through a gastrointestinal tube in her throat to keep her alive during her final days.

In addition to the gastrointestinal tube, the source said the coroner found “ample” evidence that the actress succumbed to stage 4 cancer. The type of cancer was not immediately clear.

“It was indicative when they did the autopsy that she was receiving medical care,” said the source. “There were no illicit substances or anything to suggest foul play.”