Things go crazy in a hurry. Sam tries to grab the boy, but fails to make contact as his hand is pulled out of the way. Fred decides that a fist to the face is safer than a knife to the palm, but John seems to disagree. The father's shoulder rams into the contractor, but doesn't knock him off balance by enough to prevent his fist from making contact.
One thing has come of it: Jason's teeth tear open his lip, and there is blood to be had.
Jason's head comes back up after taking the Punch, his eyes completely black, devoid of iris or white. "Fine. Lets be that way!" he says, then throws his hand forward. It doesn't touch Fred, but that doesn't stop the man from flying back against the wall.
*** Inside Jason's head ***
Jason watches all this happen, and in retrospect, it is obvious that the demon had some sort of telekinetic ability.