He thought that the door would detect anything and that would prevent the door from closing. What better way to test this hypotheses than by using your head. He sticks he head between the closing door and the body of the van. He soon realizes that he messed up.
The door continues to close and he get’s stuck. Luckily it doesn’t appear that the Salesman’s neck was severely injured. Although I’m not sure that he will be showing his face around anytime soon. Comment below if you would have done this!