I think it is, yes.
Targeting civilians who've had nothing to do with him? Check.
Doing it so to advance an ideological/political goal? Check.
Attempting to spread terror among the members of the targeted group? Check.
Thus it is terrorism.
That the victims were picked based on their race simply makes it a hate crime along with being an act of terrorism, sort of like how Hezbollah will target Jews from outside Israel to advance its agenda against Israel or how the Islamic State targets non-Sunnis from all around the world.