Clearly Partridge faked his own death because he is Red John.

Why did no one come when Theresa Lisbon called for assistance? Because Red John told them to wait until he told them it was okay to show up. Red John made sure only his followers would arrive at the scene so he could fake his own death. Theresa was there to distract Patrick Jane from inspecting Partridge's body. That is why he drew the smiley on her face.