You follow the RA without question.
TCAS doesn't paint an exact picture of where traffic is, just a guide, the traffic you see may not be the traffic generating the RA.
Don't be lulled into a false sense of security because you can see something out of the window that corresponds with TCAS traffic, that will KILL YOU.
ALWAYS FOLLOW THE RA DON'T EVEN THINK ABOUT DOING ANYTHING ELSE.