"When he put on the suit and the helmet went on, it was like magic," the Black Panther designer said following one of Chadwick Boseman's first fittings

Ruth Carter is honoring the late Chadwick Boseman and looking back on one magical career moment.

The famed costume designer, who won an Oscar in 2019 for her work on Black Panther, is reflecting on some of the moments she shared with Boseman while working with him on the history-making Marvel movie and 2017's Marshall. 

"I started to work on Marshall with Chadwick and didn't even think about [Black Panther]," Carter tells PEOPLE before explaining that she wanted to focus on the job at hand, getting Boseman prepared to take on the role of Thurgood Marshall.  "I went through the fitting process with Chad — he had a lot of changes. Thurgood Marshall was very dapper in his young days, so we dressed him really dapper. He was a lot of fun. But I understood from our fitting that he really did want to come together on this and understand the period, understand what his role was."

While working on the mid-century-set movie, Carter, 60, says she played a lot of YouTube videos of the period, so the actors could see and get a real sense of how people wore the clothes at the time, helping to mentally and physically set the stage for their characters.

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Credit: Courtesy Ruth Carter; Alexander Tamargo/Getty
ABC's Coverage Of The 91st Annual Academy Awards - Red Carpet
Ruth E. Carter
| Credit: Getty
Chadwick Boseman in Marshall

"He enjoyed it. He had done James Brown prior to this, so he loved to do that the sex machine move with his feet," she says referring to Boseman's 2014 film, Get on Up.  "Though, he felt a little strange, because he felt like he didn't look like Thurgood Marshall. We were doing our interpretation of the great Thurgood Marshall."

Still shooting Marshall, Carter later found out she had landed the Black Panther costume designer gig but decided that she didn't want to tell Boseman right away.

"I wanted to just keep it quiet and then, towards the end of the shooting, I finally revealed my secret," the designer recalls, soon discovering that her secret wasn't a secret at all.  "And Chad said, 'I already knew.' He said it was that little smirky smile on his face."

She continues, "He said, 'You killed it Ruth, you killed it.' So I felt really good that I was able to hold it. But he was also able to hold the secret too."

After their time on Marshall, Boseman — who died on Aug. 28 following a private years-long battle with colon cancer at the age of 43 — and Carter began working together on the film that would not only make history but forever immortalize the actor as a superhero.

Marvel Studios' BLACK PANTHER Black Panther/T'Challa
Chadwick Boseman as King T'Challa in Black Panther
| Credit: Marvel

Looking back on one of her first fitting's with Boseman for the Black Panther suit, Carter reflects on the moment the actor brought the yet-to-be-perfected costume to life.

"I had the pants suit in my office and it was dressed on a mannequin, and I thought, this thing doesn't look all that great, partly because the mannequin was weird," she recalls. "I called Chadwick in and I asked him to put the suit on — we needed to see if there were any problems or anything — and when he put on the suit and the helmet went on, it was like magic. I could see the power of these superheroes. I could see how they have an effect on people just because it's like they are a superhero."

Over time, Carter worked with the actor to perfect the iconic costume that would go on to inspire millions.

"I think that relationship ... there was so much trust because we'd worked on Marshall together. There was so much trust when we started Black Panther," she says. "It was an incredible experience because he didn't doubt anything. He always greeted me with a smile, a hug and cooperation."

Ruth Carter
Credit: Courtesy Ruth Carter

Another trait Carter admired Boseman for was his sense of community — something she strongly believes in and demonstrates through her involvement with the Boys and Girls Clubs of America.

As an alumna of BGCA the How Stella Got Her Groove Back designer has recently partnered with the organization, along with Toyota and The Coca-Cola Company, for their Workforce Readiness initiative. The initiative's goal is to help guide and prepare underrepresented kids for the workplace by giving them real-life experiences and skills needed to achieve their career goals, beyond their surrounding circumstances.

Crediting the BGCA for helping to inspire her love for design, Carter says the organization was "an integral part" of her adolescent life.

"As a young woman growing up, I started to understand how some of the skills that I was learning there were going to actually help me when I decided to go to college or as I learned the different activities — there were lessons behind the lessons," she tells PEOPLE. "The lessons that you learn are not only lessons of swimming or sewing, they're also lessons of life. I think that's what supported me as a young person growing up within the Boys & Girls Club and also supported my family and my mother."

Ruth Carter
Ruth Carter at Boys & Girls Clubs of America Alumni Hall of Fame ceremony
| Credit: Courtesy Ruth Carter
Ruth E. Carter and Eddie Murphy

Carter adds, "I was raised in a single-parent household. My mom encouraged me to stay connected to the Boys & Girls Club, which was a huge support to her as a single mother for her children to grow and be enriched."

And whether she's working alongside famed director and good friend Spike Lee, dressing Dolemite Is My Name star Eddie Murphy, or designing the world of Wakanda, Carter explains that she applies those lifelong BGCA lessons to her work.

"I was always told don't worry about the ribbon. Don't worry about the big prize ... Only know in your mind that you can do this. This was my speech long ago when I was inducted into the Boys & Girls alumni and that is something that I had carried throughout my life," she says. "If you're not focused on 'oh my God, this is Marvel. How did I get here?' You just have to attack it ... You just take it one step at a time."