The actor had been "ignoring" a lump on his neck so his girlfriend took him to the hospital, the actor's manager tells PEOPLE

Dustin Diamond died on Monday morning at age 44, but the Saved by the Bell actor wasn't alone during his final moments.

Diamond's girlfriend of one year, Tash Jules, was by his side when he died, the actor's longtime manager Roger Paul tells PEOPLE.

Paul says that Diamond had been "feeling out of sorts and he'd had a lump on his neck that he was ignoring" before he was diagnosed with stage 4 small cell carcinoma, a cancer that commonly occurs in lungs, but can also manifest in the prostate or gastrointestinal tract.

"He was afraid of the public attention if he went into the hospital. But finally, his girlfriend took him and the doctors confirmed it was cancer," Paul says.

dustin diamond
Dustin Diamond
| Credit: Chris Polk/FilmMagic

Paul adds that Diamond, who was best known for playing Samuel "Screech" Powers on the original Saved by the Bell, tried his best to remain positive while undergoing treatment.

"Of course he was scared, but he tried to find the humor in it. He did chemo — he tried everything possible. But it didn't work," the manager says. "Dustin tried to be as positive as he could throughout everything — that's who he was — but he was scared."

"He didn't want to die," Paul adds.

RELATED: PEOPLE Every Day Discusses Dustin Diamond's Death

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Diamond was diagnosed with the "brutal, relentless form of malignant cancer only three weeks ago," his rep told PEOPLE earlier on Monday.

"In that time, it managed to spread rapidly throughout his system; the only mercy it exhibited was its sharp and swift execution," his rep said. "Dustin did not suffer. He did not have to lie submerged in pain. For that, we are grateful."

Diamond's rep confirmed the actor's cancer diagnosis to PEOPLE on Jan 14. The actor started chemotherapy a week later.

Several of Diamond's Saved by the Bell costars wished him well on social media after the news of his cancer diagnosis broke, and after his death Monday shared tributes to the actor.

"Dustin, you will be missed my man. The fragility of this life is something never to be taken for granted. Prayers for your family will continue on..." wrote Mario Lopez on Instagram.

Diamond was one of the six core cast members of the beloved teen sitcom, which ran for four seasons from 1989 to 1993 on NBC. Unlike the others, he did not reprise his role for the Peacock reboot of the series, which debuted its first season in November 2020.