Richard Childress was fined $150,000 on Monday for assaulting Kyle Busch, the latest incident in an ongoing feud between NASCAR's most polarizing driver and Childress' race teams.

NASCAR also placed Childress on probation through the end of the year, finding the team owner solely at fault for Saturday's incident at Kansas Speedway. The 65-year-old grandfather apparently approached Busch after the Trucks race, placed him in a headlock, and punched him several times.

"We feel this action is appropriate and are confident all parties involved understand our position on this matter and will move forward appropriately," NASCAR said in a statement.

Childress, who dodged a suspension from NASCAR, was upset that Busch had bumped into Joey Coulter on the cool-down lap after the race.

He said in a statement that he accepts the penalty, but he did not apologize for his actions.

"First of all, I'm responsible for my actions, plain and simple," he said. "As you know, I am a very principled person and have a passion for what we do at Richard Childress Racing. I believe passionately in defending my race teams and my sponsor partners. In this instance, I let that passion and my emotions get the best of me.

"I accept the penalty NASCAR announced today and, as a company, we will now focus on this week's races at Pocono Raceway and Texas Motor Speedway."

It's not clear what probation means in relation to Childress as a car owner. Generally considered to be nothing more than a slap on the wrist, NASCAR chairman Brian France defined probation last month as "a different set of eyes and expectations" for drivers, adding they would have limited flexibility on the race track.

For Childress, it could only mean he must stay away from Busch for the rest of the year.

Busch and Kevin Harvick, RCR's top driver, have feuded on and off for years, and the tension was reignited last month after a race at Darlington. A move by Busch late in the race caused Harvick to wreck with teammate Clint Bowyer, and Harvick tried to express his displeasure after stopping his car in front of Busch on pit road after the race.

Harvick tried to punch Busch while Busch was still seated in his car, but Busch instead rammed Harvick's car out of the way so he could drive off. Harvick's car turned into the pit road wall.

Both Busch and Harvick were fined $25,000 each for the incident, and placed on probation through June 15.

But it was apparently the final straw for Childress, who let it be known he would not tolerate Busch damaging any more RCR equipment. So after racing Coulter hard in the closing laps at Kansas on Saturday, Busch bumped into the 21-year-old on the cool-down lap, presumably to show his displeasure over something Coulter had done during the race.

The act is fairly common in racing, and likely happens between two drivers following every event.

Still, it appeared to be the final straw for Childress, who according to some reports, removed his watch and handed it to grandson Austin Dillon before approaching Busch.

"I wonder if Pop Pop will get a senior citizen discount on his fine?" Dillon posted on his Twitter page after the penalty was announced.

NASCAR met individually Sunday morning with Busch, his team owner Joe Gibbs, and Childress, before announcing that Busch played no role in the altercation and was not at fault for anything that occurred. All the blame was placed on Childress, who was allowed to stay for Sunday's race because NASCAR determined his four-car organization would be without leadership if the owner was kicked out.

Childress was limited, though, as to where he could go inside the track and he spent much of the event watching from atop one of his team haulers.

Busch said he didn't believe he'd done anything to warrant the altercation.

"I don't know that I did anything out of the ordinary that would provoke something of Mr. Childress," said Busch, who seemed to indicate he would not press charges against Childress. "I'm going to leave it up to NASCAR and let them decide what they feel is best."

It was just four years ago that Childress was high on the list of team owners pursuing Busch after his release from Hendrick Motorsports. Despite his immense talent, his immaturity had made him expendable when Rick Hendrick had a chance to sign Dale Earnhardt Jr.

Team owners then lined up to sign Busch, and Childress was at the front of the charge. He defended Busch during the entire process, and didn't shy away from chasing him despite the rivalry between Busch and Harvick.

"You have to remember his age — I can name you eight or 10 guys in here at his age that were a handful," Childress said during Busch's 2007 free agency. "He's learning. Every new experience, you get educated a little more and I'd say this has educated him a little more.

"Kyle is a very young, talented race driver like many, many I've seen come up and be like that. Kyle has got a great future ahead of him. Age, time, everything, it all comes with experience."

Busch ultimately signed with Joe Gibbs Racing, and has won 17 Sprint Cup races and a Nationwide Series championship since. He's a consistent championship contender, and is currently ranked fifth in the standings — right behind Harvick.