[Prison Break]!!....What is Kellerman acting in the drama??

Kellerman was an agent of Secret Service in US. He is absolutely a bad guy. He killed so many people. He also wanna kill Sara in Season 2. However, something changed in season 2 EP13. He saved Michael and Linc. I saw the trailer of season 2 EP14. He would bring them to Terrance (brother of the President) in Montana. I don't know whether he is good or bad now.