McBell
Unbound
So the music triggered their violent outburst.Sadly I have dealt with several people who, because of their unstable mental states, have told me that they believe a piece of music was specifically "talking" to them and so reacted the way they did. I'm was only responding to Druidus' comment Simply hearing violent phrases does not cause people to do violent things.
You yourself have pointed out that they were unstable to begin with.
So really, the only conclusion one should come up with is that music can trigger violent behavior in those who are mentally unstable.
I have heard nothing that suggests that the music caused the violence, only that it triggered it.