San Diego Mosque Attack: FBI Links Teen Gunmen to Online Radicalisation

The Federal Bureau of Investigation (FBI) has linked the deadly attack on a mosque in California to online radicalisation and extremist hate networks , as investigators continue probing how two teenagers accumulated a large arsenal and carried out a hate-motivated mass shooting.

Authorities identified the attackers as Cain Clark (17) and Caleb Vazquez (18), who met online and later discovered they lived in the same area. Officials say their ideology developed through digital extremist spaces , where they shared white supremacist beliefs and broad hostility toward religious and minority groups before targeting the Islamic Centre of San Diego.

Investigators recovered a large weapons cache , including around 30 firearms, ammunition, tactical gear and a crossbow from two residences linked to the suspects, raising questions about planning, access and oversight failures. Authorities also confirmed a lengthy manifesto, reportedly about 75 pages , containing racist, antisemitic, misogynistic and anti-LGBTQ+ content, along with references to past mass attackers. The pair allegedly called themselves the “Sons of Tarrant,” referencing the Christchurch mosque shootings.

New findings show one suspect’s mother had alerted police hours before the attack , reporting he was missing, suicidal and had taken weapons and a vehicle, but the shooting still occurred shortly after.

During the assault, the gunmen opened fire at the Islamic centre, where a security guard engaged them in a gunbattle that delayed their entry and triggered a lockdown , preventing access to classrooms with over 140 children. Officials said this intervention likely prevented a far larger massacre. Three men were killed, including a long-serving guard and community members who helped draw the attackers away.

The suspects later died by suicide. Officials said there was no prior specific threat to the mosque, though they acknowledged rising hate crimes targeting religious sites across the United States. The FBI said the investigation continues into online influences, warning signs and broader extremist networks.