I explain the situation. Major Luna try a shoot on señor Massacre. As a result, can Massacre use his switch (taunt) to target another mini tha Luna?
All Actions including Attacks which are a special type of action require Targets. Major Lunah can shoot two different ways. When she uses her "Called Shot", that is an Attack so that her Target can defend himself by rolling dice. If the Target is Señor Massacre he has a chance of getting his universal Switch of which would allow him to Taunt his Target which would be Lunah. In the Reference Guide it states that during an Attack , the Attacker becomes the Defender's Target. He would not be able to taunt another character because his Switch allow him to Impose only on his Target. If Lunah uses her Action Supressive Fire, she can target Massacre but this Action is not an Attack so that he rolls no dice and so cannot gain to use his Switch.
Let's compare Laxmee's D/BUff3r and hEXx3r's Gotcha!: The subtle difference between Laxmee and hEXx3r is that Switches of Laxmee affect "a Target" and the Switches of hEXx3r affect "to the Target". So you can choose any Target for Switches of D/BUff3r and you can only choose the original Target for Gotcha! to apply its Switch.