For nearly three quarters on Saturday night, referee John Parry and his crew kept a lid on extracurricular activity at Paul Brown Stadium. The Pittsburgh Steelers and Cincinnati Bengals were still intense and had plenty to say to each other, but the floodgates opened with one especially brutal hit late in the third quarter -- one that transformed the game into a mess of dirty and angry play that ultimately made the difference in the Steelers' 18-16 victory in the wild-card playoffs.

As we all try to process exactly what happened, let's answer some questions involving the major events from that point on:

Why wasn't Steelers linebacker Ryan Shazier penalized for a hit that appeared to knock out Bengals running back Giovani Bernard?

In short, Shazier should have been.

With 1:43 remaining in the third quarter, Bernard made a two-yard catch and took enough steps to become a runner -- thus stripping his protection as a defenseless receiver. Shazier, however, then lowered his head and hit Bernard's helmet. Shazier could have done so legally under certain circumstances, but he made at least one and possibly two mistakes on this play that should have been penalized.

The first was a violation of NFL Rule 12, Section 2, Article 6(i), which defines unnecessary roughness as "using any part of a player's helmet or facemask to butt, spear or ram an opponent violently or unnecessarily." Given the force of Shazier's hit, it would be hard to argue against that definition.

Second, it's debatable whether Shazier could have been penalized for initiating contact with the crown of his helmet outside of the tackle box, a violation of Rule 12, Section 2, Article 8. The rule defines the tackle box as "an area extending from tackle to tackle and from three yards beyond the line of scrimmage to the offensive team's end line." Per the unofficial game statistics, Bernard was two yards beyond the line of scrimmage.

In either event, Bernard lost a fumble on the play. A call for either of these penalties would have returned the ball to the Bengals.

Vontaze Burfict could have easily been flagged for running up the tunnel after intercepting Landry Jones. EPA/MARK LYONS

Why wasn't Bengals linebacker Vontaze Burfict penalized for an excessive celebration?

With 1:36 remaining in the game, Burfict intercepted Steelers quarterback Landry Jones, was ruled down by contact and then ran 85 yards in the other direction and into the tunnel of the stadium. Several teammates followed him.

Rule 12, Section 3, Article 1(e) prohibits two or more players from "engaging in prolonged, excessive, premeditated or choreographed celebrations or demonstrations." Article 1(d) of that rule defines excessive or prolonged as celebrations that continue after a warning from an official.

Because Burfict was on the move all the way into the tunnel, the guess here is that no official had a chance to give him a warning.

How will the NFL react to Burfict's hit on Steelers receiver Antonio Brown?

With 22 seconds remaining in the game, Burfict threw a shoulder into Brown's helmet as Brown stretched for the ball. It was a clear violation of the NFL's rule against hitting the head of defenseless receivers, and Parry's crew penalized Burfict 15 yards.

He is a repeat offender here, having been fined nearly $70,000 for hits and penalties in the Bengals' Week 14 game against the Steelers. Given the continued pattern, and the egregious nature of his hit on Brown, it wouldn't be a surprise if Burfict is suspended to start the 2016 season.

Update: The NFL is in fact likely to suspend Burfict next season, possibly for more than one game, according to ESPN's Adam Schefter.

Why was Steelers assistant coach Joey Porter on the field after the hit on Brown?

It is not unusual for coaches to check on injured players, but typically that's done by the head coach or a player's position coach. Porter was neither in this case, of course, and someone on Parry's crew should have directed him off the field.

Given the intensity of emotions for both teams as Brown lay on the ground, it's not surprising that Parry's crew prioritized other potential flare-ups. But Porter soon found himself in the middle of the jawing that eventually provoked Bengals cornerback Adam Jones to commit a penalty that gave the Steelers an easy game-winning field goal.

Update: The NFL will fine Porter for his actions, according to Schefter.

What did Jones do?

Parry announced only that Jones had engaged in unsportsmanlike conduct, and a review of the television broadcast video was not conclusive. Jones appeared to be yelling at Porter at a time when Parry, umpire Mark Pellis and field judge Buddy Horton were all in between Porter and Jones.

As Jones became angrier, he might have bumped Horton's back. Even if he didn't, Rule 12, Section 3, Article 1(b) prohibits the use of "abusive, threatening or insulting language."

What could Parry's crew have done differently?

Parry was the referee for the teams' Week 14 slugfest, and he was clearly prepared for high intensity and emotion Saturday night. Members of his crew stood at the 50-yard line during pregame warmups to avoid any fights. Together, the officials called a total of 19 penalties during the course of the game -- including four for unsportsmanlike conduct and three for unnecessary roughness.

But the failure to make a call on Shazier's third-quarter hit seemed to raise emotions to a higher level. The game quickly got out of hand. Parry would have been more than justified for ejecting Burfict following the hit on Brown, but that play was too late in the game to regain any control.

These teams walked onto the field in a simmering cauldron of violence, and it didn't take much for it to boil over.