After high school, Gilliard says, he went to Juilliard to continue his study of classical clarinet, expecting a career as a concert musician.
"The plan was to go Juilliard, graduate and then go across the street and play in the New York Philharmonic — that was the plan, anyway."
But he says that started to change when he "woke up one day" and felt like "he didn't want to practice" any more.
"And that's when you start to worry," he says. "Why did I not feel like practicing today? So I started wondering what was going on. And, basically, you feel like you're going insane. You're in one of the greatest arts schools in the world, and you're not wanting to participate. So I really started looking around."
Gilliard says he saw a pattern to his young life. While at the BSA, he went to all the plays that his classmates staged. And now he was doing the same at Juilliard.
"And I thought, 'Hmmmm, maybe there's something there that I need look into. And I went and took an acting class outside of Juilliard and found I had a passion. Yeah, and so I just jumped on that train — followed that path."
Gilliard has appeared in more than 30 feature films and made-for-TV movies, included John Waters' "Cecil B. Demented" and "Gangs of New York," since he started professionally in 1991. He's also appeared in such TV series as "Homicide: Life on the Street,' "Friday Night Lights" and "Army Wives."
But it is his work as D'Angelo in "The Wire" for which he is most widely known. His superb performance in Season 1 played a significant role in helping establish the series critically.
He cherishes the memories of being part of an outstanding ensemble that included Idris Elba, Dominic West, Wendell Pierce and so many other fine actors — even as he laughs about living at the home of his mother, Edith Gilliard Canty, while filming.
"I actually did, because she wouldn't have it any other way," he says. "You know, if I'm in Baltimore, I've got to be at home — in my old room."
He says it was "weird" that first season, because growing up, he had lived in "West Baltimore in the Franklin Square area very close to the Lexington Terrace projects where the Barksdales were operating" in "The Wire."
"I actually played football for the Lexington Terrace projects," Gilliard says. "It's really crazy that I came back and did that particular show."
At middle age, Gilliard seems very clear about the mentors and moments of passage in his life.
"The Baltimore School for the Arts changed my life, it really did," he says. "But before the School for the Arts, I was still living in West Baltimore and could have gone in another direction."
Along with his mother, he says, there were four strong male figures who helped guide him to the right path: his stepfather, Curtis Canty; a Franklin Square Boys Club director named Lonnie Fisher; and neighbors James Reeves and Frank Wheeler.
"What the School for the Arts taught me was a great work ethic," Gilliard says. "They showed me — not just taught me — that if you work hard, you can see the effects. They gave me that lesson, and I have used it at every stage of my life. And I am still using it now in my new role on 'The Walking Dead.' "
Season 4 of "The Walking Dead" begins at 9 tonight on AMC