When you're sitting on the toilet, playing a game on your phone and feeling like the king of the world . . . SUDDENLY GETTING SHOT through the wall doesn't seem like a possibility.  But that actually happened in Utah.

--Back on December 20th, in Taylorsville, Utah, 27-year-old Christian Paul spotted a MOUSE and decided to kill it . . . by SHOOTING IT.  So he grabbed his nine-millimeter and fired a shot at the mouse.

--He missed, of course . . . but the bullet went through the kitchen wall into the bathroom . . . and hit his roommate in the CHEST.  The roommate was hospitalized in serious condition, but he survived.

--Christian was arrested for the shooting, and is facing a felony firearms charge.

--But that wasn't the only arrest that came out of this idiotic incident.  While the police were there, they found a 13-year-old girl hiding in the basement . . . and arrested a third roommate, 34-year-old Daniel Kunzler, for being an A-HOLE SEXUAL PREDATOR.

--He's been charged with a ton of felonies related to sexual abuse of a minor.