I think a true terrorist is someone who is motivated on behalf of an outside cause.
This can be hard to determine because I think when caught, some will plead mental health issues.
I don't think we should necessarily look at the outcomes because an attack (for whatever reason-on behalf of a cause or for personal mental health reasons) can have different results, depending on how competent the attack was, how well planned etc
So whether one person was killed or 100 does not necessarily determine if it was a terrorist act (in my opinion).
We need to listen to what the attackers themselves claim. There have been some who do claim to be acting on behalf of a cause, religious or otherwise. This is not to say the person may not also have mental health issues, I think sometimes a cause might appeal to such a person, make them feel accepted, part of a group.
But if they attack on behalf of a cause, then it is terrorist inspired.
If they attack for personal reasons, which i think has happened a few times in US, where disgruntled students with a grudge have stormed in to kill fellow students, then that may be mass murder but it is not terrorism per se. The idividual often ends up committing suicide at the end.
To me, terrorism is an attack performed on the general public for political or religious or idealogical reasons.
The farmers who wipe out their families etc, not terrorism. Mass murder for private reasons.
