I think the first thing would be a strong anger. the word is weak !!)
I'll go to see this person , put my anger aside, tell this person how dangerous he is, if he really realize what he(she) is doing .
I also would try to know who he (she) met to tell them, so they would be able to receive a treatment.
It's rather difficult for me to denounce in public but I'll do every thing to stop this person to go on doing that.......by talking, by trying to help him (her) to get a treatment and to realize he (she) may kill some one .....
hope I helped !
