The car bombing outside a California fertility clinic that killed one person and injured four others appears to have been driven by anti-natalist ideology, according to two senior law enforcement officials briefed on the incident.

The suspect, identified by authorities as Guy Edward Bartkus, is believed to have carried out Saturday’s explosion, which resulted in his own death.

Investigators are focusing on social media posts made by the suspect, including a 30-minute audio recording, which they say support anti-natalist views. While the posts and the recording are still being verified, officials believe they reflect the ideology behind the bombing. Anti-natalism refers to the belief that no one should have children.