This is why Ryan Shazier wasn't flagged for head shot to Gio Bernard

It's been tough sledding for the Bengals in Saturday night's wild-card matchup against the Steelers, and this play late in the third quarter sent the Cincinnati players -- and their fans in Paul Brown Stadium -- into a tizzy:

On first glance -- and second and third glance -- it sure looks like Steelers linebacker Ryan Shazier should have been flagged for this shot to the head against Gio Bernard, who dropped to the turf and fumbled on the play.

But a flag was never thrown and, it turns out, it was the right call.

To recap: once Bernard take two steps, he's no longer considered defenseless, and high hits are perfectly legal ... or was it?

UPDATE: As several people have pointed out, while Bernard does, in fact, become a runner after two steps, Shazier used his helmet "to butt, spear or ram an opponent violently or unnecessarily," which is a violation of Rule 12, Section 2, Article 6(i). 

And then there's this rule, which could have also applied:

Rule 12, Section 2, Article 8. Initiating Contact With the Crown of the Helmet. It is a foul if a runner or tackler initiates forcible contact by delivering a blow with the top/crown of his helmet against an opponent when both players are clearly outside the tackle box (an area extending from tackle to tackle and from three yards beyond the line of scrimmage to the offensive team’s end line). Incidental contact by the helmet of a runner or tackler against an opponent shall not be a foul.

Either way, things got worse for the Bengals; the Steelers challenged the play and after an official review, Pittsburgh was awarded the fumble, too.