Sad news to report, as Jimmy Kimmel’s real-life “Uncle Frank” Potenza, a former NYPD officer and security guard who worked on camera on Kimmel’s ABC talk show Jimmy Kimmel Live, died today. He was 77.

Information about a memorial service is forthcoming.

Kimmel’s TV show already had just begun a two-week hiatus, not due back on the air until Sept. 6, 2011, the Tuesday after Labor Day. A message sent out to staff and crew today informed them that “Uncle Frank” passed in the early morning hours Tuesday at Cedars Sinai Hospital “surrounded by his loving family,” adding: “His huge heart and joyous spirit will live on in each and every one of us at JKL forever.”

Potenza served in the military in the Korean War, then worked for 20 years as a police officer in New York City, another two decades as a security guard at Caesars Palace in Las Vegas, and five more years keeping watch at St. Patrick’s Cathedral in NYC.

Kimmel personally asked his Uncle Frank to move to Hollywood and join his brand-new TV talk show in January 2003, serving as both an actual security guard as well as an on-air contributor.

Back in May, Uncle Frank taught his nephew Jimmy and the audience about geography to help viewers figure out about the places where Prince William and Kate honeymooned after their royal wedding. Roll the clip.

On Twitter today, Jimmy Kimmel was RT’ing fans who expressed their sentiments about Uncle Frank, and added himself: “thank you for your kind words about a very kind man.”

Cousin Sal, meanwhile, said on Twitter: “I will miss my Uncle Frank dearly. A great man, friend, comedian.”

He wanted to share this clip of “Grandpa Frank and Grandma Chippy” reading a story to their then-future grandchild in December 2010. Roll it.

Potenza is survived by his three daughters and newborn granddaughter Franki.