Authorities called the attack terrorism and said Bartkus left behind nihilistic writings that indicated views against procreation, an idea known as anti-natalism.

One person was found dead, and the FBI said it was sending investigators, including bomb technicians, to the scene.

Bruce Springsteen’s criticisms of Donald Trump last week appear to have triggered the president even further, as he is now calling for an investigation of the superstar singer’s endorsement of Kamala...