John Boyega found it difficult to "comprehend" the death of his childhood friend Damilola Taylor.
The schoolboy was stabbed to death in Peckham, London, at the age of ten, and John has confessed to being "shaped" by the tragedy.
During an appearance on BBC Radio 4's 'Last Word', John said: "Even though I was young, it was a shock to understand how mortality worked.
"To think that somebody as young as me could pass away in such a horrific way was hard for me to understand or comprehend.
"And I definitely think [Damilola's death] has shaped me through the years and just affected my perspective on certain things."
The murder case attracted a huge amount of interest and discussion in the UK, but John previously made a conscious decision to refrain from speaking about it publicly.
The London-born actor explained: "I'm quite private in general, but with this specifically, it's that celebrity thing of not wanting to get in front of very real-life news."
John remembers his childhood friend as being "flamboyant and charismatic".
And the actor still has vivid memories of his last day with Damilola in November 2000.
John said: "From the hours we left him in Peckham to the hours when I went home, and then the police were at our door and there was a whole investigation that we were involved in, was definitely life-changing for me, definitely altered my perspective."
John actually felt inspired to become an actor after listening to a poem that was read at Damilola's funeral.
He explained: "What is truly my dream? Do I have the guts to identify what my dream is? Am I too young to identify my dream and work towards it?
"And after reading that poem, I was just like, yeah, I have no excuse. I want to be a movie star."
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