He was 40 years old.
Phillips was a member of the Memphis rap group Three 6 Mafia.
According to his Facebook Page, Phillips was on life support due to an aneurysm.
He later died Friday.
Phillips is the second member of Three 6 Mafia to die in two years.
Ricky Dunigan, known as Lord Infamous, died in December 2013.
“To all who are concerned Robert Cooper Phillips aka Koopsta Knicca has officially left us all. This is a great lost to us all. We will continue to keep him alive with his music,” a page administrator to Phillips’ Facebook page said.