You could also drag K off to the sideline and shoot him, but that may be somewhat excessive. From your description, KCI seems a legitimate call, and takes care of everything. If the receiver had not clearly completed the Fair Catch prior to being contacted (touched it then muffed it) See Case Book 6-5-6-E, you may not have anything. This is truly your judgment call.
The contact, judged legal or illegal, happened either while the ball was live, or after it became dead. It can't be both.
The objective is to fit a proscribed penalty to an action, if called for, not fit the action to a variety of penalties to exact a certain level of punishment. It's not personal, it's business.