Friends going to do school shooting!?

Ok so I have these 2 friends. They are Indian like me. Ive known them ever since Kindergarten but they have gotten bullied seriously over years and it still continues with jocks calling them names and girls making fun of them also. Anyways they were bullied verbally ,racially and physically. Now im in my last year of high school and so are they. Anyways they are currently seeing a psychologist in school because of their problems but this doesn't seem like its helping. Both of them are pissed off at the jocks and popular girls for humiliating them throughout their 4 years of high school, so in return they want to do a school shooting which im terrified of. Both of these guys invited me to join them on their spree they said they dont have access to guns but they are going to bomb the school because the bullies called them terrorist because of their nationality. They also said that since they will kill themselves after the bombs go off they want me to plant two more bombs so all the people they didnt kill who are going to waste will also die. They want to bring in 4 propane bombs put them all on the main entrance floor so its enough to collapse the entrance floor of the school. They already laid out a set of instructions and Maps on how the attack will take place. They are purchasing the items at a local hardware store with money from their part time jobs and their savings. I think their really going to do this what should I do please give me advice!