03/12/2014 AT 02:45 PM EDT
Tanya Brown remembers that day in June 1994
as if it were yesterday: waking up to her sister Denise's anguished screams, rushing to her and struggling to comprehend when Denise cried, "She's dead! He killed her! Coco's dead!"
It was the morning after the brutal murders of 35-year-old Nicole
– whom the family called Coco – and her friend Ron Goldman outside Nicole's Brentwood condo, murders her ex-husband, football legend O.J. Simpson, would be charged
with, resulting in the year-long "trial of the century" that transfixed the nation and ultimately ended in Simpson's acquittal
Only 24 at the time, Tanya struggled with depression for years afterwards, coming close to suicide and spending time on a psych ward.
In a new memoir/self-help book, Finding Peace Amid the Chaos: My Escape from Depression and Suicide
, Brown, now 44 and working as a life coach and mental-health advocate, opens up about her journey and how she survived.
The book, excerpted exclusively in this week's PEOPLE, includes never-before revealed details about the Brown family's nightmare:
Their visit to Nicole's condo the day after her murder, when they came upon a relative "standing [outside] with a garden hose, washing away what was obviously blood, hoping that he’d get it all cleaned before we got out there";
O.J.'s pre-trial phone call to Tanya from jail, insisting "You know I loved your sister, right? C'mon ... I would have taken a bullet for her";
And Tanya's gradual, horrifying realization that "Uncle O.J." might be a vicious, cold-blooded killer.
Today, Brown, who has a masters in counseling psychology, says she has forgiven O.J.
"I don't forget, but I do forgive. So I can move on."
She wrote the book, she says, to encourage others who've been through traumas. "This whole thing is about changing lives and giving people hope," she says. "There's joy after pain, but you have to let the anger go."
For more on Brown and her book, be sure to pick up this week's PEOPLE