Gabrielle Union Shares Sweet Memory of Late Director John Singleton: 'He Will Be Sorely Missed' (Exclusive)

The actress opened up to ET about her friendship with the filmmaker, who died Monday at the age of 51.

In the wake of director John Singleton's untimely death on Monday at the age of 51, celebrities from every corner of the world have been sharing their stories, tributes and memories of the late filmmaker.

Among the stars sharing heartfelt memorials was Gabrielle Union, who shared a particularly sweet story about meeting Singleton through her older sister, and how he became a friend of the family and ultimately chaperoned her 18th birthday.

"Well, I think most of us know him as, you know, a famed director, the youngest director ever nominated in Academy history. I know him as my older sister's cool friend from USC," Union told ET's Keltie Knight during a recent interview. "I just know a different side of him… and how dynamic and amazing he was."

The America's Got Talent judge also marveled at the late two-time Oscar-nominated director's "amazing very fun, loving, inclusive spirit."

"He was a great, great man and he will be sorely missed," Union said. "It's just a reminder, you know, to sort of understand, acknowledge, and familiarize yourself with the warning signs of strokes."

"Prioritize your own health, be your own best advocate," she added. "Just treat each day like it could be your last, because it just may be."

Singleton died Monday after suffering a stroke earlier this month. Following the news of his passing, hundreds of his friends, fans and former colleagues took to social media to celebrate his memory and mourn the loss.

For more on the groundbreaking filmmaker's life, legacy and indelible mark on the movie industry, watch the video below.