Actor Ryan O'Neal punched his 22-year-old son Redmond, knocking him out, during a violent argument in the Los Angeles gym the Oscar nominee owns. O'Neil, a former amateur boxer, lashed out because he suspected recovering addict Redmond was using drugs again, reports the National Enquirer.

A source tells the tabloid of the December 26 bust-up, "It happened in Pro Gym, the workout facility that Ryan owns, in front of 30 witnesses."

The Enquirer reports that Redmond, who had just ended his 12th stint in rehab, had stolen and forged a $500 check from his father, and attempted to cash it.

Last February, O'Neil was accused of attacking Redmond's half-brother Griffin and his then-pregnant girlfriend with a fireplace poker.

(This news article provided by World Entertainment News Network)