There is a theory that the Sheriff recruited Rigsby for tiger tiger when they met in episode 2, well my reply is

Rigsby joined forces with a man he knocked him down to the floor for what he saw as trying to kill Van Pelt ?

Also Van Pelt would know he had a tattoo.

And before there's anymore bollocks about Van Pelt being a RJ accomplice remember she killed that Craig guy she was going to marry who was an RJ accomplice - why do that if she's an RJ friend ?

Cheers