Complex sentence: Mulder and Scully have Wetzel guard her while they assist the cops in the raid of a crack house, but are summoned back outside when Wetzel again encounters the entity, wildly shooting at it.
Split into simpler sentences: Mulder and Scully have Wetzel guard her while they assist the cops in the raid of a crack house. However, they are drawn back outside when Wetzel again encounters the entity, wildly shooting at it.