He was identified as John T. Earnest, a Rancho Penasquitos resident. He is being questioned by homicide detectives.

Earnest appears to have written a letter posted on the Internet filled with anti-Semitic screeds. In the letter, he also talked about the planning the attack.
“How long did it take you to plan the attack? Four weeks. Four weeks ago, I decided I was doing this. Four weeks later, I did it.”
Earnest, who is white, wrote that he was willing to sacrifice his future “for the sake of my people.”
Poway Mayor Steve Vaus called it a “hate crime,” based on statements the shooter was heard making as he entered the synagogue.

Earnest had no criminal record and no prior contact with law enforcement, Gore said. He had no known connections to any white supremacist groups.

He had written a manifesto, which was being reviewed by investigators, along with his social media posts.

Sheriff Gore said investigators were looking into possible ties between Earnest and a fire at the Dar-ul-Arqam Mosque on 6th Avenue in Escondido in March . Graffiti left behind by the suspect made reference to the mass shooting of Muslims in New Zealand.