Who is Bill Ayres? and why is he not in jail?

I am 30 years old as a result I am not old enough to remember the turbulent 60's and the I am limited to my knowledge of the Vietnam Era. If Bill Ayres is who I am led to believe he is, through various media outlets, why is he not in jail for bombing the US Capital or Pentagon. I like to believe that I am a smart guy who does not buy into microwave politics, however if Ayres is a criminal then should he not be in jail and if so why not?