when the perp is in the "in group" he's a lone wolf, when he's not he's a terrorist. simple really.
and white lunatic doesn't count as a terrorist, but dylan roof or eliot rogers does.
Checkout http://www.armslist.com/. The first time I bought a gun it was eye-opening: email a random person, give them cash, drive back with a gun.
So easy it's scary.
Similarly, an attack can be lone-wolf at the same time as being a politically-motivated attack.