FBI Says Teen Gunmen Who Killed Three Outside Islamic Center of San Diego Met on Accelerationist Message Board, Co-Wrote 75-Page Manifesto Praising Christchurch Shooter Brenton Tarrant

SAN DIEGO — The two teenagers who opened fire outside the Islamic Center of San Diego on Sunday morning, killing three men before turning their guns on themselves, met online through a fringe accelerationist message board and shared a 75-page manifesto that espoused Islamophobia, antisemitism, anti-Trump views and admiration for the 2019 Christchurch mosque attacker, FBI officials said Tuesday. The bureau identified the shooters as Cain Clark, 17, of El Cajon, and Caleb Velasquez, 18, of Chula Vista. The attack is being investigated as a hate crime and an act of domestic terrorism.

The shooting began at 9:42 a.m. Pacific Time on Sunday, May 17, in the parking lot of the mosque on Eckstrom Avenue in the Clairemont neighborhood, just as Sunday school was letting out. The three victims, all killed before the gunmen could enter the building, were identified as Amin Abdullah, 51, a security guard hired by the mosque after a 2017 vandalism incident; Mansour Kaziha, 64, a longtime maintenance manager who had worshipped at the center for 26 years; and Nader Awad, 39, a member of the congregation who lived across the street and ran outside when he heard the first shots. San Diego Mayor Todd Gloria, in a Monday morning news conference flanked by mosque board members and the city's police chief, called the killings "the most painful day in this city's modern history."

Clark and Velasquez exchanged more than 11,000 direct messages on Discord and Telegram in the eight months before the attack, FBI Assistant Director in Charge David Adams told reporters Tuesday. The two never met in person until the morning of the shooting, when Clark drove Velasquez from his Chula Vista home to a Home Depot parking lot in Mission Valley, then on to the mosque in a 2014 Toyota Camry registered to Clark's mother. Authorities recovered two AR-15-style rifles, a 9mm handgun and approximately 1,800 rounds of ammunition from the vehicle. Phrases including "hate speech" and the names of three prior mass shooters were scrawled in marker on the rifles' magazines.

The 75-page document that the FBI confirmed was authored by Velasquez and edited by Clark was posted to a now-deleted Telegram channel approximately 40 minutes before the attack and includes praise for Brenton Tarrant, who killed 51 worshippers at two mosques in Christchurch, New Zealand in 2019, as well as denunciations of "globalist Trump," feminism, Jewish people and the LGBTQ community. "They didn't discriminate on who they hated," Adams said. "The radicalization here was broad, online, and accelerated by the algorithms of platforms we have warned about for years."

President Donald Trump ordered flags lowered to half-staff through Friday and called the attack "a vile act of evil against innocent Muslim Americans worshipping their God." The Council on American-Islamic Relations announced a $200,000 reward fund for any tipsters whose information leads to charges against possible co-conspirators, and the Department of Homeland Security raised the threat advisory for U.S. houses of worship to its highest level since the October 2018 Tree of Life synagogue shooting in Pittsburgh. Funeral services for the three victims will be held at the Islamic Center on Friday after midday prayers.