Before Cory Monteith was Finn, the jock-turned-Glee club member, he was a troubled child from Vancouver Island.

On his search for direction in life, he wandered into Andrew McIlroy's acting class and both their lives changed forever.

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McIlroy talked to " Good Morning America" Wednesday about Monteith.

"Cory walked in off the street, into a room where acting was happening and never left," said McIlroy, who gave Monteith free acting classes in exchange for cleaning McIlroy's acting studio.

Cory would clean up the studio and in exchange Mcilroy would give him free acting classes.. That's how their friendship

The two never lost their connection. In fact, McIlroy became one of Monteith's dearest friends. They would often take long walks together.

The popular star of "Glee" died in Vancouver on Saturday of a mixed drug toxicity involving heroin and alcohol, according to the British Columbia Coroners Service. Monteith was 31 years old.

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His death has been hard on McIlroy.

"I don't like to talk about him - I don't want him to be a past tense …," he told "GMA." "It was a shock, it's always a shock. You live with hope. I never walked away from Cory thinking 'Oh my God, I hope you're OK."'

Monteith sat in one of McIlroy's acting classes shortly before his death. He sat in the studio with his hat pulled down low, wanting to soak up the experience without being noticed by anyone. He gave no indication of a man slipping back into addiction, McIlroy said.

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"I think we just have to understand that the disease of addiction makes you think you're driving the car and then it slowly moves you into the passenger side and it starts to drive …

"It just lies in wait," he said. "Cory tried really, really hard to keep it at bay."

McIlroy said Monteith wasn't hanging around with a bad crowd, but rather, was spending time with old friends he'd acted with years ago. He'd just come off doing a solo nature hike in the woods and he wanted to see those old friends before he returned to Hollywood for the new season of "Glee."

He never quite understood his stardom, McIlroy said.

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"Even though you love me, I don't know that I deserve it and even though you like my show, I don't know that I'm very good at it," McIlroy recalled Monteith saying.

"He was surprised at every compliment he got. And grateful for every compliment he got," McIlroy added.