"He approached the clerk and demanded money from the register. The clerk, afraid for his safety, gave O'Neal cash from the till," LAPD Detective Meghan Aguilar told the New York Daily News.
Officers responding to the scene located the Hollywood heir in the area and made the arrest.
"Officers found the knife and cash in O'Neal's possession," Aguilar said.
O'Neal, 33, was booked on a felony robbery charge late Tuesday and was being held on $50,000 bail as of Wednesday afternoon.
O'Neal has struggled with drug addiction for years and racked up a series of drug-related arrests stretching back a decade.
He was in jail and at a court hearing the day his mother died in June 2009 and was briefly released to attend her funeral.
His half-sister Tatum O'Neal also has struggled with addiction and told People magazine in 2015 that she was extremely worried about his safety.
"I love him, but I have never seen a more scary side of addiction," she said.
"He's got addiction problems so bad that it breaks my heart," she continued. "Nobody knows what to do with Redmond. From what I've seen, there is no way he's going to survive."
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