Ideally we'd wait until we have evidence of who did it and what their motivations are, rather than just jumping to whichever conclusion fits our existing biases.
On the other hand, we don't live in an ideal world. If it is terrorism, then the perpetrators have an interest in avoiding capture so there's probabilities of false negatives as well as false positives.
We know that people who espouse terrorism not only fantasize but produce instructional materials on this sort of thing, so we should admit admit it as a possibility and try to estimate the probability of it being a factor here.
https://www.justice.gov/opa/pr/three-men-plead-guilty-conspi...
Three Men Plead Guilty to Conspiring to Provide Material Support to a Plot to Attack Power Grids in the United States
Domestic Terrorism Plot was in Furtherance of White Supremacist Ideology
Sure are an awful lot of coincidences. Guess we’ll never know.