They play came with 7:20 left in the third quarter. The Browns snapped the ball on their own 38-yard line and quarterback Seneca Wallace tried to hit tight end Evan Moore down the field. The ball -- and Chiefs safety Kendrick Lewis -- arrived 22 yards down the field.
Lewis hit Moore as he was reaching for the ball -- a/k/a a defenseless receiver -- leading with what appeared to be his shoulder. It's hard to tell in the replays if he first made contact with Moore's body or his helmet.
Either way, multiple flags came out and Lewis was tagged with a personal foul for "contact to the helmet of a defenseless receiver."
A quick Google search shows that there are plenty of times when receivers have been fined for a hit on a defenseless receiver. I'm not sure what the standards are for who is and is not fined but the fact that the result is a concussion -- a major point of emphasis this year for the NFL -- probably doesn't help his case.
We'll see what the NFL thinks. And that goes for the alleged incident surrounding Chiefs defensive end Shaun Smith. If the NFL thinks they're guilty (i.e. fined), then they're guilty. If they don't, then they're not guilty.