I used the word 'crazy', rather than mentioning mental health issues. 'Crazy' does not just refer to people with mental health issues, if refers to irrational acts.
To expand on my point, some of these small-scale 'terrorist' attacks show very little evidence of being coherently planned, and it's difficult to believe that an organised terrorist group is behind them. It seems more likely that some of these acts were performed by people acting alone, or vulnerable people provoked to it - and yes, some of these people may well be mentally ill; that hardly means they cannot be capable of violence.
