Christopher "Big Black" Boykin, cast member of "Rob & Big," is dead at 45

"Rob & Big" star Christopher "Big Black" Boykin has died.

ET can confirm that the 45-year-old entertainer and musician passed away on Tuesday morning. There is no news yet on cause of death, however, TMZ reported that "multiple people connected to Chris ... believe it was a heart attack."

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Boykin and his best friend, skateboarder Rob Dyrdek, starred in their eponymous MTV reality show from 2006 to 2008.

The Mississippi native was also Dyrdek's bodyguard, and the series followed their adventures, from holding an exorcism to breaking Guinness world records, including eating the most powdered doughnuts eaten in less than 3 minutes.

Boykin also appeared on Dyrdek's other MTV shows, including "Ridiculousness" and "Rob Deryk's Fantasy Factory."

Dyrdek paid tribute to his friend and colleague on Twitter.

"My heart is broken," Dyrdek wrote in the caption of a photo of him and Boykin sitting together on a large swing. "I don't want write this post. I don't want to believe that this is reality. I am so thankful for you."

He added, "We truly were brothers that lived an unexpected unforgettable adventure. I just can't fathom that it would end so suddenly. You will forever be in my heart." 

He also tweeted a photo of Boykin cradling Dyrdek's 10-month-old son, Kodah Dash and wrote, "I am so thankful for this moment... thank you for being an amazing human being and brother."

On Tuesday, Boykin's "Fantasy Factory" co-star, Chanel West Coast, tweeted her condolences, writing, "RIP @BigBlack. My heart is crushed. I'll remember all the times you made me laugh and my prayers go out to your family."

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The former U.S Navy serviceman is survived by a 9-year-old daughter, Isis.