Guy Fieri Shares News of Dog's Death the Day Before His Birthday: 'Today Is the Saddest Day'

Jesse Grant/Getty; Guy Fieri/Twitter Guy Fieri, Cowboy

Guy Fieri and his family are mourning the loss of their dog, Cowboy, who died shortly before the Food Network star's 55th birthday on Jan. 22.

"Today is the saddest day in the Fieri family," Fieri posted, alongside a photo of the pup, on Twitter Saturday. "We lost our COWBOY today. He was one-of-a-kind and brought so much love and energy to our family."

The restaurateur's heartbreaking post garnered support from famous friends such as Star Wars legend Mark Hamill, who responded with a broken-hearted emoji, and Seinfeld and Dancing with the Stars alum John O'Hurley, who posted "The O'Hurleys share your sadness. It is the loss of innocence. May God celebrate him Home."

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Guy Fieri/Twitter Cowboy

A day after sharing the sad news about Cowboy's death, Fieri celebrated his 55th birthday on Sunday.

The Guy's Grocery Games creator posted a video on Instagram showing how he spent his birthday. In the clip, Fieri sings along to "I Can't Drive 55" with Sammy Hagar.

"The greatest birthday of my life. Wow. Thanks to all my friends family and my big brother the Red Rocker @sammyhagar. Wow. UNBELIEVABLE," Fieri captioned the video.

For Fieri, his family, including its four-legged members, always comes first.

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"Family is always the first priority," Guy told PEOPLE in September. "Most of my friends will [say] I haven't changed. I think it's because when I got into television, I'd already done what I wanted to do. I wanted to be a great dad."

Along with their two sons, Hunter, 26, and Ryder, 17, the Diners, Drive-ins and Dives host, and his wife, Lori, helped raise nephew Jules, 23, following the death of Guy's sister Morgan in 2011 from melanoma.

Part of being a great dad for Guy means instilling his strong work ethic in all three men.

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"He's always leading by example," Hunter told PEOPLE of his dad. "Seeing how much he cares and how, even though he is so busy all the time, he focuses a lot of effort on doing fundraisers . . . it's eye-opening to me."