The question of what is and what is not ‘terrorism’ becomes most contentious when it’s not a Muslim doing the killing.
The reason is that there are clearly plenty of Islamic terror attacks, and far fewer for any other religion or ideology, and Muslims and other apologists for Islam don’t like it that Islamic terrorism gets so much attention. They’d like non-Islamic non-terrorist attacks to be called terrorist attacks, or they’d like the world to make less of the ‘Islamic’ in Islamic terrorism (“Nothing to do with Islam”, “Not a true Muslim”, “Terrorism has no religion”, …). And when the real world doesn’t comply, they make fake claims about ‘Islamophobia’ and ‘racism’.
Is there a lone killer, that’s crazy (crazier than run of the mill crazy ideologues) and is he unaffiliated with a particular group or acting without sanction from a particular group?
He’s a crazy lone wolf killer.
Is he doing it in the name of his ideological group in order to strike terror into the target?
He’s a lone wolf terrorist.