Investigators on Sunday identified a 25-year-old man as the suspect in the bombing outside a fertility clinic in Palm Springs, Calif., as they searched for the motive behind the blast that damaged several blocks downtown and, they believe, killed him as well.

The suspect, Guy Edward Bartkus of Twentynine Palms, Calif., had “nihilistic ideations,” authorities said, and had specifically targeted the clinic. Officials called the bombing an act of terrorism and said they were examining writings that could be related to the attack, which happened on Saturday.

On a website that promotes the idea of terminating life, an audio recording features a man who said he was going to bomb an in vitro fertilization clinic because he was angry at his own existence.

Three people familiar with the investigation said agents are examining that website to try to verify whether the bomber had made those statements.

On Sunday, Richard Bartkus, 75, the father of the suspect, said he believed the voice on the recording was his son’s. Mr. Bartkus, of Yucca Valley, Calif., said that he had not seen his son in 10 years and that he had no idea his son had held opinions of the kind voiced on the recording. Earlier, Mr. Bartkus had said he was shocked when a relative texted him on Saturday that his son had been implicated in the bombing.

Although officials did not say that Guy Bartkus was the lone suspect, they did say that they were not actively searching for others. They also said on Sunday that there was no continuing threat to the community involving this attack.