. >> reporter: carl donaldson is a science teacher at this rural colorado high school.een carrying a 9 millimeter gun in his classroom for a year. >> where is your firearm. >> can i show it to you? >> yes, please. >> cowboy boots. >> is it loaded? >> there's not one in the chamber. he volunteered to be armed making him about one of 100 armed staff in schools across colorado. >> would it be more effective to have a loaded gun? >> yes. that's a concern, especially if they come after me. >> reporter: teachers are required to go through training. >> there's a really good chance if you were to have an active shooter it would be one of your current or former students. are you ready to shoot them or possibly kill one of them? >> if someone point as gun at my or my students, yes. i'm not going to hesitate. >> reporter: we sat down with a few other teachers here during a lunch break having the same discussion. >> i had mixed feelings when we first came up with it. it was like, yes, we do need help, but i'm not a huge gun person either. so i had the mixed feelings. >> reporter: d