Like many others, comedian Jerry Seinfeld is struggling to come to terms with the unexpected death of Joan Rivers.

The comedienne had agreed to appear on his web series "Comedians In Cars Getting Coffee" before she passed away on Sept. 4, reports Us Weekly.

Sadly, family, friends and colleagues are already missing Rivers horribly.

Seinfeld took to his Facebook page to share with fans the sadness he felt as he came across an old text confirming River's excitement to be the first guest on his show.

"I just came across this heartbreaking text on my phone from August 19th," the funny man wrote. "I had asked Joan Rivers to be our lead guest on the new season of Comedians in Cars, and she was thrilled."

"Then we got a call saying she was going in for a medical procedure and needed to postpone," he added.

After complications at that medical procedure during an operation on her vocal cords at Yorkville Endoscopy clinic on Aug. 28, Rivers stopped breathing. A week later, the "Fashion Police" star was pronounced dead and the comedy world would never be the same again.

"I would have loved to have shown another side of her, I wanted to tell her how much I admire all she had accomplished, especially in the latter stages of her career," Seinfeld said. "She was one of the greats. I'll miss her," he concluded.

Daughter Melissa Rivers announced her mother's death on Sept. 4, according to Us Weekly, releasing a statement thanking everyone who was there for her saying, " [I want to thank] the doctors, nurses and staff of Mount Sinai Hospital for the amazing care they provided for my mother" and the "outpouring of love, support, and prayers we have received from around the world."

"My mother's greatest joy in life was to make people laugh. Although that is difficult to do right now, I know her final wish would be that we return to laughing soon," said Melissa Rivers.