Brady had just thrown an interception in the end zone, giving Washington an opportunity to tie the game on a final drive. When he went to the sideline, he was confronted by O'Brien.
The coordinator seemed to take exception with Brady telling his intended receiver, Tiquan Underwood, to "go and get it." This set off O'Brien, who began screaming at his star quarterback. Brady gave it right back, yelling that Underwood was open and peppering his shouts with profanities.
O'Brien was eventually separated from Brady by Bill Belichick.
The two men embraced minutes later after the Patriots clinched the game with an interception of their own. Brady took responsibility for the incident in his postgame press conference.
"I threw a pretty bad interceptions, so he wasn't happy about it," Brady said. "Probably a long line of coaches and players that were pretty pissed at me after that, but Billy got to me first. He let me have it. I deserved it."