A pressure cooker was used to make the bombs used in the Boston Marathon Bombing. However, besides cooking, there appears to be another form of pressure cooker used by the government. Pressure cookers use steam to build up pressure to increase the rate at which something cooks. It changes the normal conditions to conditions that have a more rapid effect on what is being, well, pressure-cooked.
KC Massey was returned to jail for violating his (innocent until proven guilty) pre-trial release conditions (Cruel and Unusual Punishments - Before Conviction). Prior to his pre-trial release, he had been held at Willacy Federal Detention Facility, and was placed in a solitary cell. After the violation, he was sent to a County Sheriff's facility, Carrizales Rucker Detention Center, under federal authority. Again, he was placed in solitary confinement.