There is no way Guillermo can get blood on the right side of his face just as Topher is seen in the same moment, same shot being electrocuted on Guillermo's left side, across the pond. However, this isn't supposed to be Topher's blood. Topher had let in some vampire assassins, which Guillermo is implied to have killed before he came to tell off Topher about letting in just anybody (Implied with this blood).
The Familiar who cleaned the gun by staring down the barrel, blowing his head off - never pulled the trigger.