The actress, 39, mourned the Sex and the City star's death in a heartfelt tribute shared to Instagram on Wednesday as she revealed she got a tattoo in his honor before seeing him for the last time.
"The world knows that @willie.garson has been a pivotal player in my life," she wrote. "So I will not be able to fully articulate my feelings here. I'm gonna need some time. @jeffreydeanmorgan and I are devastated."
"Willie was a romantic friend," Burton continued. "Deeply thoughtful. Intentional with his effort and attention and devotion. Social media is ablaze right now with evidence of that … each person in his life felt special. Spoiled, even. Willie most definitely spoiled me."
The One Tree Hill alum's touching post included a series of pictures celebrating Garson, including a close-up of the new tattoo on her arm featuring the words "calm down."
"He would pay you the biggest compliment in the world ... And right as you'd blush, he's temper it with, 'Alright, calm down!' And then laughter," Burton recalled of her late friend. "He'd stop you before you could rebuff the compliment. Calm down. I can hear him saying it."
"Before I went to see him, I needed him to know how I felt," she continued. "And @hudsonvalleytattooco was so kind and understanding and got me in the night before my flight. I wanted Willie to know that I was carrying that 'calm down' with me forever."
Hilarie Burton/instagram (2)
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Burton also shared that Garson wrote a book prior to his death, which she promised to get published "for his son Nathen."
"It is a love letter to our industry, to storytelling and to the hundreds of people he worked with and made better over the decades," she concluded. "To Willie's family, especially @nathen_garson… on my honor I will see it through. You have been so generous in sharing him with the rest of us. Love you."
Burton and Garson starred together on USA's White Collar, which aired from 2009 to 2014. Garson played Mozzie, while Burton, who joined the cast in 2010, played Sara Ellis.
Garson, who had been suffering from pancreatic cancer, died surrounded by family on Tuesday afternoon. He was 57.
He famously played Stanford Blatch, the best friend of Sarah Jessica Parker's Carrie Bradshaw, in HBO's Sex and the City and its spinoff movies. He is also set to appear in the upcoming reboot And Just Like That... on HBO Max.
In a statement to PEOPLE, a spokesperson for HBO/HBO Max said Garson was a "bright light" for those who were fortunate enough to know him.
"Willie Garson was in life, as on screen, a devoted friend and a bright light for everyone in his universe. He created one of the most beloved characters from the HBO pantheon and was a member of our family for nearly twenty-five years. We are deeply saddened to learn of his passing and extend our sincere condolences to his family and loved ones."