Not terrorism?

Imagine… a person leaves behind a politically charged manifesto, and then flies an airplane into a crowded office building with the intent of killing himself along with many other people. A terrorist?

Not according to the United States government, who promptly assured us that the incident that occurred today in Austin, Texas, is not terrorism-related.

So what exactly defines terrorism? Does the perpetrator have to be, in addition to a politically motivated suicidal murderer, also brown-skinned and of the Muslim persuasion?