"I was playing there for about an hour and everything was going smoothly," Manning, 37, told reporters at Friday's Vanity Fair and L'Oreal Paris DJ Night, hosted by Hailee Steinfeld, in Los Angeles.
Then things changed: "I always shout out people that I miss that have died," Manning said. "I was playing 'Lose Yourself' by Eminem, who I was in a film with, and put my fader down and gave it up to Brittany and then everything went dead [silent].
"Nobody tripped over a chord or anything. It was very bizarre."
In that moment, the Orange Is The New Black star immediately knew it was Murphy.
"Brittany's in the house," Manning said that night, according to video obtained by TMZ. "That was one of my best friends and we lost her over terrible, terrible things, and I think she just wanted a moment of silence right now."
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Even on normal nights, "I think about her all the time," Manning said of Murphy.
"It was probably one of the hardest things I have ever dealt with, seeing one of my friends, my fellow actresses pass away like that," Manning said.
Still, she won't let her memory go. Manning said she worked through her grief, in part, by "celebrating [Murphy] and remembering her."
"Once people die, people forget and that bothers me," Manning said.