John T. Earnest, the 19-year-old man detained in Saturday’s deadly synagogue shooting in San Diego, was a student at Cal State University San Marcos, school officials said.

Earnest was being questioned by the FBI and homicide authorities. San Diego Sheriff William Gore said authorities were poring over his social media accounts and a letter that Gore described as a “manifesto” posted online around the time of the attack.

Gore said officials were working to verify the posting’s authenticity and did not offer details on any motive. But the letter supposedly details the shooter’s hateful motivations and his reasons for targeting members of the Jewish faith.

In the letter, posted on an online text storage site called Pastebin, the author identified himself as a 19-year-old nursing student with the same name as the suspect.

It said in part: “I can already hear your voices. ‘How could you throw your life away? You had everything! You had a loving family. You had great friends. You had a church. You were doing well in nursing school. You could have gone so far in your field of study. You could have made so much money and started a happy family of your own.'”

On Saturday evening, San Diego Police had cordoned off the streets near what was believed to be Earnest’s home, some 7 miles southwest of the Chabad of Poway synagogue. Gore, the sheriff, said deputies were serving a search warrant at his home.

Gore said in a tweet that authorities had found “no prior contact” between law enforcement and Earnest.

San Diego Police Chief David Nisleit said that as one of his officers was on the way to the shooting at Chabad of Poway, he overheard on the scanner that the suspect had called into police, saying “he was just involved in this shooting” and giving his location along Interstate 15.

The officer quickly spotted the suspect, who pulled over and jumped out of his vehicle with his hands up, surrendering to authorities.

A rifle was found in the front passenger seat, Nisleit said.

Karen Haynes, president of Cal State San Marcos, said in a letter to the campus community: “We are dismayed and disheartened that the alleged shooter – now in custody – is a CSUSM student. CSUSM is working collaboratively with the San Diego County Sheriff’s Department to assist and gain more information.” CSUSM is about 12 miles northwest of Chabad of Poway.

She added: “We extend our deepest condolences to all of the victims, their families, friends and our entire community. We share your grief. This despicable act is entirely against our values as a University, particularly given that many in our community are preparing to observe Yom HaShoah (Holocaust Remembrance Day) on May 1. We stand in solidarity with the Jewish community and reject the rhetoric of divisiveness that feeds hatred.”

Gore, the sheriff, said Earnest was also being investigated in connection with an arson at a mosque in nearby Escondido last month. In that incident, a fire broke out at 3:15 a.m. on Sunday, March 24, at Dar-ul-Arqam mosque, also known as the Islamic Center of Escondido.

The suspect in that attack left behind a note referencing the terrorist attacks at two mosques in Christchurch, New Zealand, that killed 50 worshippers in mid-March. The letter that investigators are investigating related to Saturday’s attack also claims responsibility for the arson at Dar-ul-Argam.

In the Escondido incident, the mosque’s security camera captured a person breaking a parking lot gate’s lock and pouring some liquid near a side door and setting it on fire. Seven people were at the mosque at the time and were able to put out the fire with a fire extinguisher before firefighters arrived. No one was injured; the FBI has offered a $10,000 reward for information related to the incident.

The Islamic Center of Escondido is about 14 miles north of the Poway synagogue attacked Saturday.

Earnest is a member of the Orthodox Presbyterian Church, said Pastor Zachary Keele, who leads the Escondido church. “It’s a deplorable act of wickedness,” said Keele. “I’m still in shock… I’m kind of numb.”

Loralee Visintainer, 29, who grew up in the neighborhood up the hill from the Earnest family, said she was in Girl Scouts with one of the suspect’s sisters, but never knew Earnest. “They’re a great family,” she said. “I feel bad.”

John Earnest had attended Mt. Carmel High School, where his father, also named John, taught science. In 2014, the school magazine published a story about students whose parents taught at the school.

In the article, the younger Earnest, who was then a freshman, said: “At lunch, I go to his classroom. I store some of my stuff inside of his room.” His father said he was happy to have two of his children enrolled in the school.

“I love it, mostly because I know that this is a great school,” the elder Earnest told the publication, “There are great teachers. There are great kids. And, I enjoy being around my children and most of the time they enjoy being around me, but it’s not really about me, it’s about the school. That’s why I am glad they are here.”

Poway Unified School District Communications Director Christine Paik confirmed in a statement that the suspect was a 2017 graduate of Mt. Carmel High School. “The words and actions of this individual are in no way representative of the beliefs held by our school community nor by his father, a long-time teacher at MCHS. Mt. Carmel is a No Place for Hate campus,” she said.

The year he graduated, John T. Earnest was honored for his academic achievements along with about 30 other Mt. Carmel classmates in a program called F.A.C.E., or Fraternity of Academic and Civic Excellence.

In a short bio posted by the program, Earnest posed in a dark suit and red tie. The accompanying text said Earnest had a GPA of 4.31, belonged to the varsity swim team, had taken many AP classes, and played the piano.

It said he had an “excellent work ethic” and wanted to major in biophysics at college.