Vin Diesel admitted to be still "haunted" by his co-star and pal Paul Walker's death, calling the incident the "darkest period of his life."
The 47-year-old actor said though growing up in the "bouncer world" had made him used to losing people, his "brotherhood" with Walker, 40 was special, which made it hard to deal with his death, the Daily Express reported.
He added that even though he is an actor, it still doesn't teach one to "mourn and pretend" at the same time to be acting with someone who they have lost.
The actors had teamed up and worked together in the The Fast And The Furious franchise since 2001.
Talking about his Guardians of the Galaxy role, he said his own personality is a lot like that of his onscreen character Groot.
The 47-year-old actor says the innocence of his alter-ego Groot, a genetically modified tree who tries to save the world in the new Marvel film, is comparable to his own off-screen persona, reports contactmusic.com.
"To maintain your innocence is a feat. So much magic comes from it. Ironically, people probably see more of Groot when I'm posting (on Facebook) than they would in any of the characters I play," he said.
Diesel's love for Facebook is visible through his regular interactions and he argues that stars ought to be more aware of the direct communication, social media allows with fans.
"Imagine if you were able to Facebook Elvis, and talk to him, and hear from him without the Hollywood of it all. That was the Fast & Furious experience," he said.