This article has been updated to reflect news developments.

Three days before a mass shooting that killed at least 21 people in El Paso, I predicted in these pages that we were on the path to a frightening uptick in white nationalistic hate violence. The El Paso terrorist appears to have been motivated by a racist ideology that cited other mass shootings, including in Christchurch, New Zealand. The F.B.I. has labeled it domestic terrorism and the governor of Texas has suggested that it be prosecuted as a hate crime. I have never felt so badly about being so right.

I made that prediction because I learned from 25 years in the F.B.I., including during a stint as head of counterintelligence, to trust my gut when I saw a threat unfolding. Now, my instinct and experience tell me that El Paso will not be the end of it, and that we are headed for more hate-based violence potentially stoked by a divisive president. (The motive for a second mass shooting on Sunday in Dayton is less clear.)

Yes, President Trump has fallen short of calling for violence against minorities and immigrants. And yes, he condemned racist violence and white supremacy on Monday. But he has yet to apologize for painting people of color as outsiders and invaders, for calling for them to be sent back to where they came from, and for asserting that no humans would want to live in certain American cities. As a consequence, he has given license to those who feel compelled to eradicate what Mr. Trump himself has called an infestation.

Since October, the F.B.I. has made 90 arrests in domestic terrorism cases. Domestic terrorism includes violence by Americans who belong to anti-government militias, white supremacist groups or individuals who ascribe to similar ideologies not connected to Islamic extremism. In fact, the F.B.I. says that of its 850 pending domestic terror investigations, about 40 percent involve racially motivated extremism. In 2017 and 2018, the F.B.I. made more arrests connected to domestic terror than to international terrorism, which includes groups like Al Qaeda and the Islamic State and their lone-wolf recruits.