Why one or the other? Your story overlooks one part of the definition of domestic terrorism that you provide: "the term “domestic terrorism” means activities that... (B) appear to be intended— (i) to intimidate or coerce a civilian population." The news thus far certainly suggests a hatred of LGBTQ people, and one might argue that death equates a form of "extreme coercion," thus fitting the definition of terrorism.
Why one or the other? Your story overlooks one part of the definition of domestic terrorism that you provide: "the term “domestic terrorism” means activities that... (B) appear to be intended— (i) to intimidate or coerce a civilian population." The news thus far certainly suggests a hatred of LGBTQ people, and one might argue that death equates a form of "extreme coercion," thus fitting the definition of terrorism.