It seems like the Charmer effect can apply to yourself if you are within the explosion radius of an enemy killed with Shovel-splosion, sometimes causing it to change you to the T side and thus making all the enemies into your friends. Which means you can only apply 1 damage per shot to the enemy until the Charmer effect applies and changes them to the CT side, and remains this way until you can get lucky enough to have the Charmer effect re-apply to yourself on the explosion and put you back onto the CT side.