In an emotional preview of his episode of VH1’s “Behind the Music,” premiering March 7 at 10 p.m., Nelly opens up about his sister Jackie’s death from leukemia. The “Just a Dream” rapper painfully recalls how family members tried to hide the severity of her illness and his final conversation with her before she passed in 2005.

“Nobody wanted to tell me how severe and how close things had gotten,” Nelly says. “She wasn’t telling me the truth, and everybody around her that knew wasn’t telling me that, ‘Yo, she’s not gonna make it.’”

His last words with Jackie took place 25 minutes before her body failed.

“She gets off the phone and she lays down and she’s gone. They said the only thing that kept her alive was that she wanted to talk to me before she left, and I was enraged,” continues Nelly, who was so distraught that he destroyed a door and a TV. “I just broke down. In one of the rare moments, I did cry.”

When Jackie was diagnosed with leukemia in 2003, Nelly established the non-profit 4Sho4Kids organization and the “Jes Us 4 Jackie” campaign to help raise awareness about the need for bone marrow donations in the African-American community.