Education advice for me?

Okay I want to be a criminal investigator, preferrably for the FBI, I also want to throw a little psychology in there so I can do interrogation and stuff like figuring out the psyche of the criminals. I know I need to study criminal justice but I want to focus more on the science part so I dont end up being a cop. What are the steps I need to take to achieve this? I just want to know what I need to major in, and the jobs I should look in to after college so I dont go down the wrong career path. Oh and I am going to Texas State by the way. I know the FBI standards are tough so I need to know everything, thanks.