The attack was stunning even for a sport known for its violence: With 8 seconds left in Thursday's game, Cleveland Browns star Myles Garrett tore off Pittsburgh Steelers' Mason Rudolph's helmet, then hit Rudolph's head with it in a fit of rage.

Had the brawl happened on a street corner, Garrett very well could have been charged with assault. But on a football field — where athletes play knowing there is a risk they will get hurt — the lines are blurry, experts say.

"If we're going to be very technical, every single thing that takes place on a football field is assault," said Tammi Gaw, an attorney and athletic trainer based in Washington, D.C., who is the founder of Advantage Rule, a consulting firm that works on sports policy. "But sports, especially contact sports, exist thanks to a doctrine of assumption of risk."

As part of the doctrine, athletes consent to the risk of injury that comes along with physical contact and are paid to consent to that. That means they are generally barred from taking legal action against their league or other players if they, for example, get hurt after being tackled because they have voluntarily exposed themselves to that possibility.

But the circumstances that cause the injury must be "reasonably foreseeable," said Anthony R. Caruso, a sports and entertainment attorney with clients in New York City and New Jersey. He called Garrett's helmet attack "shocking" and said various factors, including the fact that it happened when the ball was out of play, could potentially lead to the incident being interpreted as outside of the bounds of the assumption of risk doctrine.

Garrett took responsibility for the altercation, calling it a "terrible mistake," and Friday, the National Football League announced it had suspended Garrett without pay indefinitely.

A spokeswoman for the Cleveland police told NBC News on Friday that there are no charges filed against Garrett "as there was no police report filed by the person hit with the helmet."

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But even if charges are filed, Caruso said courts generally prefer for athletic leagues to be the ones handling offenses that happen on the field.

"Many times, judges aren't close enough to the game itself to be a fair tribunal," he said. "The courts defer to the leagues to regulate their own players and participants with suspensions."

"The courts defer to the leagues to regulate their own players and participants with suspensions."

He said he could recall one case 40 years ago where a judge allowed an NFL player to proceed to trial for violence on the field: Hackbart v. the Cincinnati Bengals. In that case, player Dale Hackbart had filed a complaint alleging he sustained serious injuries when another player, Charles Clark, intentionally struck him during an emotional outburst because Clark's team was losing.

The court ruled that Hackbart knew he was getting into a dangerous profession by signing up for football. But ultimately in 1979, the U.S. Court of Appeals for the 10th Circuit ruled in Hackbart's favor, arguing that this was not the type of injury he expected to receive.

It is not clear if the helmet hit would be considered a foreseeable injury, especially because the assumption of risk can mean different things depending on the specific situation, said Justin Spizman, an attorney with Hawkin Spizman Fortas, a criminal defense and personal injury law firm in Atlanta.

"The lines become blurred," he said. "You have to look at what sport you're playing. Is it a foreseeable consequence? The ones in golf are much different than the ones in football. And what are the facts that led to it?"

Video of the altercation shows Rudolph "putting his hands on Garrett first," Spizman said, which could potentially give Garrett the ability to argue he was acting out of self-defense. And other players also joined the melee, meaning theoretically other players than just Garrett could be charged.

Still, Spizman added, "Rudolph obviously didn't deserve to get smacked in the head with a helmet."

Violence during games has led to charges in other sports. In 1988, Dino Ciccarelli became the first National Hockey League player to receive jail time for hitting another player with his hockey stick. Boston Bruins defenseman Marty McSorley was charged in 2000 with assault with a weapon for his actions during a game. In baseball, Jose Offerman was sued in 2009 for hitting two players with a bat in a minor league game.

And there have been plenty of instances of athletes facing charges for attacking fans or for other violence involving players before or after a game.

It was not clear how badly Rudolph was injured from the helmet hit, which could be another factor critical in determining whether charges are necessary, the experts said, especially if he doesn't have any lasting injuries at all.

But Garrett's attack could be a "tipping point," Caruso said, for criminal prosecutors who want to get involved in football cases.

"I could see a trend where judges are going to start getting involved if the violence is so egregious and the league isn't containing it as they should," he said.