The Cradle 2 the Grave star was a 19-year-old shop assistant in 1992 when she was assaulted one evening as she was closing up the shoe store.
The rapist forced Union and a co-worker into a back room, where he raped the actress.
And she insists she would not be alive today if it weren't for important lessons she learned from watching Winfrey's daily talk show.
She explains, "Luckily, Oprah had a show about what to do in case you're a victim of a violent crime.
She adds, "At some point he put the gun down and calmly asked me to hand him the gun and, at that point, I was like, 'Oh, it's me or you, and it ain't gonna be me today. I'm about to kill you.'
"I grabbed the gun, I spun around and did the best I could trying to kill him."
The actress missed her attacker when she shot at him and this led to a fight for the gun, which left her black and blue. The rapist fled and later turned himself in to police after another rape attack.
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